diff --git a/README.md b/README.md
index 553f8ee873..0f44fc3b6d 100644
--- a/README.md
+++ b/README.md
@@ -32,7 +32,7 @@ of the project.
 
 ```html
 <!DOCTYPE html>
-<html>
+<html lang="en">
   <head>
     <title>Network</title>
     <script
diff --git a/cypress/pages/events-target.html b/cypress/pages/events-target.html
index dc8b8aeff8..c4f722ebb2 100644
--- a/cypress/pages/events-target.html
+++ b/cypress/pages/events-target.html
@@ -1,5 +1,5 @@
 <!DOCTYPE html>
-<html>
+<html lang="en">
   <head>
     <title>Vis Network | Cypress | Events Target</title>
 
diff --git a/cypress/pages/pollution.html b/cypress/pages/pollution.html
index 1d1f722063..dee63b25f9 100644
--- a/cypress/pages/pollution.html
+++ b/cypress/pages/pollution.html
@@ -1,5 +1,5 @@
 <!DOCTYPE html>
-<html>
+<html lang="en">
   <head>
     <title>Vis Network | Cypress | Pollution</title>
 
diff --git a/cypress/pages/universal.html b/cypress/pages/universal.html
index 21a6309cdb..76dfcce4f0 100644
--- a/cypress/pages/universal.html
+++ b/cypress/pages/universal.html
@@ -1,5 +1,5 @@
 <!DOCTYPE html>
-<html>
+<html lang="en">
   <head>
     <title>Vis Network | Cypress | Universal</title>
 
diff --git a/docs-kr/index.html b/docs-kr/index.html
index 885a6d79eb..21f3dd58cb 100644
--- a/docs-kr/index.html
+++ b/docs-kr/index.html
@@ -1,5 +1,5 @@
 <!DOCTYPE html>
-<html>
+<html lang="ko">
   <head>
     <meta charset="utf-8" />
     <meta http-equiv="refresh" content="0;url=network/" />
diff --git a/docs/index.html b/docs/index.html
index fb736ca198..04478b3499 100644
--- a/docs/index.html
+++ b/docs/index.html
@@ -1,5 +1,5 @@
 <!DOCTYPE html>
-<html>
+<html lang="en">
   <head>
     <meta charset="utf-8" />
     <meta http-equiv="refresh" content="0;url=network/" />
diff --git a/examples/network/basicUsage.html b/examples/network/basicUsage.html
index d5e3a204f5..412a7a0094 100644
--- a/examples/network/basicUsage.html
+++ b/examples/network/basicUsage.html
@@ -1,5 +1,5 @@
 <!DOCTYPE html>
-<html>
+<html lang="en">
   <head>
     <title>Vis Network | Basic usage</title>
 
diff --git a/examples/network/basic_usage/esnext.html b/examples/network/basic_usage/esnext.html
index 63c36ed1fc..af49750289 100644
--- a/examples/network/basic_usage/esnext.html
+++ b/examples/network/basic_usage/esnext.html
@@ -1,5 +1,5 @@
 <!DOCTYPE html>
-<html>
+<html lang="en">
   <head>
     <meta charset="utf-8" />
     <title>Network | Basic Usage | ESNext Build</title>
diff --git a/examples/network/basic_usage/legacy.html b/examples/network/basic_usage/legacy.html
index f0c894304f..be833e9a4f 100644
--- a/examples/network/basic_usage/legacy.html
+++ b/examples/network/basic_usage/legacy.html
@@ -1,5 +1,5 @@
 <!DOCTYPE html>
-<html>
+<html lang="en">
   <head>
     <meta charset="utf-8" />
     <title>Network | Basic Usage | Legacy Build</title>
diff --git a/examples/network/basic_usage/peer.html b/examples/network/basic_usage/peer.html
index 8e039ae5d3..cf1dc77969 100644
--- a/examples/network/basic_usage/peer.html
+++ b/examples/network/basic_usage/peer.html
@@ -1,5 +1,5 @@
 <!DOCTYPE html>
-<html>
+<html lang="en">
   <head>
     <meta charset="utf-8" />
     <title>Network | Basic Usage | Peer Build</title>
diff --git a/examples/network/basic_usage/standalone.html b/examples/network/basic_usage/standalone.html
index cebd6f2c51..5649ded414 100644
--- a/examples/network/basic_usage/standalone.html
+++ b/examples/network/basic_usage/standalone.html
@@ -1,5 +1,5 @@
 <!DOCTYPE html>
-<html>
+<html lang="en">
   <head>
     <meta charset="utf-8" />
     <title>Network | Basic Usage | Standalone Build</title>
diff --git a/examples/network/data/datasets.html b/examples/network/data/datasets.html
index ea346c3d3f..5363dea4c7 100644
--- a/examples/network/data/datasets.html
+++ b/examples/network/data/datasets.html
@@ -1,5 +1,5 @@
 <!DOCTYPE html>
-<html>
+<html lang="en">
   <head>
     <title>Vis Network | Data | Dynamic Data</title>
 
diff --git a/examples/network/data/dotLanguage/dotEdgeStyles.html b/examples/network/data/dotLanguage/dotEdgeStyles.html
index 02baad7fea..83d7b0f352 100644
--- a/examples/network/data/dotLanguage/dotEdgeStyles.html
+++ b/examples/network/data/dotLanguage/dotEdgeStyles.html
@@ -1,5 +1,5 @@
 <!DOCTYPE html>
-<html>
+<html lang="en">
   <head>
     <title>Vis Network | Data | DOT edge styles</title>
 
diff --git a/examples/network/data/dotLanguage/dotLanguage.html b/examples/network/data/dotLanguage/dotLanguage.html
index b42a5c2c70..77be46363c 100644
--- a/examples/network/data/dotLanguage/dotLanguage.html
+++ b/examples/network/data/dotLanguage/dotLanguage.html
@@ -1,4 +1,5 @@
-<html>
+<!DOCTYPE html>
+<html lang="en">
   <head>
     <title>Vis Network | Data | DOT Language</title>
 
diff --git a/examples/network/data/dotLanguage/dotPlayground.html b/examples/network/data/dotLanguage/dotPlayground.html
index f3c7f1321e..c5dce419e6 100644
--- a/examples/network/data/dotLanguage/dotPlayground.html
+++ b/examples/network/data/dotLanguage/dotPlayground.html
@@ -1,5 +1,5 @@
 <!DOCTYPE html>
-<html>
+<html lang="en">
   <head>
     <title>Vis Network | Data | DOT language playground</title>
 
diff --git a/examples/network/data/dynamicData.html b/examples/network/data/dynamicData.html
index e9dfb69caa..0766ec6a4a 100644
--- a/examples/network/data/dynamicData.html
+++ b/examples/network/data/dynamicData.html
@@ -1,5 +1,5 @@
 <!DOCTYPE html>
-<html>
+<html lang="en">
   <head>
     <title>Vis Network | Data | DataSet</title>
 
diff --git a/examples/network/data/dynamicFiltering.html b/examples/network/data/dynamicFiltering.html
index 37fd368469..bf41fd58e9 100644
--- a/examples/network/data/dynamicFiltering.html
+++ b/examples/network/data/dynamicFiltering.html
@@ -1,5 +1,5 @@
 <!DOCTYPE html>
-<html>
+<html lang="en">
   <head>
     <title>Vis Network | Data | Dynamic filtering</title>
 
diff --git a/examples/network/data/importingFromGephi.html b/examples/network/data/importingFromGephi.html
index 446eb89940..b5e5e49949 100644
--- a/examples/network/data/importingFromGephi.html
+++ b/examples/network/data/importingFromGephi.html
@@ -1,6 +1,6 @@
 <!DOCTYPE html>
 <!-- saved from url=(0044)http://kenedict.com/networks/worldcup14/vis/ , thanks Andre!-->
-<html>
+<html lang="en">
   <head>
     <meta http-equiv="content-type" content="text/html; charset=UTF8" />
     <title>Vis Network | Data | Importing from Gephi (JSON)</title>
diff --git a/examples/network/data/scalingCustom.html b/examples/network/data/scalingCustom.html
index daa13c5ef2..c9312e6ac3 100644
--- a/examples/network/data/scalingCustom.html
+++ b/examples/network/data/scalingCustom.html
@@ -1,5 +1,5 @@
 <!DOCTYPE html>
-<html>
+<html lang="en">
   <head>
     <title>Vis Network | Data | Custom Scaling</title>
 
diff --git a/examples/network/data/scalingNodesEdges.html b/examples/network/data/scalingNodesEdges.html
index 306e589ccd..da1763295c 100644
--- a/examples/network/data/scalingNodesEdges.html
+++ b/examples/network/data/scalingNodesEdges.html
@@ -1,5 +1,5 @@
 <!DOCTYPE html>
-<html>
+<html lang="en">
   <head>
     <title>Vis Network | Data | Scaling Nodes and Edges</title>
 
diff --git a/examples/network/data/scalingNodesEdgesLabels.html b/examples/network/data/scalingNodesEdgesLabels.html
index be6a1783dd..c721f8b5c0 100644
--- a/examples/network/data/scalingNodesEdgesLabels.html
+++ b/examples/network/data/scalingNodesEdgesLabels.html
@@ -1,5 +1,5 @@
 <!DOCTYPE html>
-<html>
+<html lang="en">
   <head>
     <title>Vis Network | Data | Scaling Labels</title>
 
diff --git a/examples/network/edgeStyles/arrowAlignment.html b/examples/network/edgeStyles/arrowAlignment.html
index 0aab0c9c1d..6047b706bd 100644
--- a/examples/network/edgeStyles/arrowAlignment.html
+++ b/examples/network/edgeStyles/arrowAlignment.html
@@ -1,5 +1,5 @@
 <!DOCTYPE html>
-<html>
+<html lang="en">
   <head>
     <title>Vis Network | Edge Styles | Arrow Alignment</title>
 
diff --git a/examples/network/edgeStyles/arrowTypes.html b/examples/network/edgeStyles/arrowTypes.html
index 6869561e7b..52a7e84a4d 100644
--- a/examples/network/edgeStyles/arrowTypes.html
+++ b/examples/network/edgeStyles/arrowTypes.html
@@ -1,5 +1,5 @@
 <!DOCTYPE html>
-<html>
+<html lang="en">
   <head>
     <title>Vis Network | Edge Styles | Arrow Types</title>
 
diff --git a/examples/network/edgeStyles/arrows.html b/examples/network/edgeStyles/arrows.html
index 1af54c3792..b3fc57a693 100644
--- a/examples/network/edgeStyles/arrows.html
+++ b/examples/network/edgeStyles/arrows.html
@@ -1,5 +1,5 @@
 <!DOCTYPE html>
-<html>
+<html lang="en">
   <head>
     <title>Vis Network | Edge Styles | Arrows</title>
 
diff --git a/examples/network/edgeStyles/background.html b/examples/network/edgeStyles/background.html
index 628edc8cfa..c61bae60b9 100644
--- a/examples/network/edgeStyles/background.html
+++ b/examples/network/edgeStyles/background.html
@@ -1,5 +1,5 @@
 <!DOCTYPE html>
-<html>
+<html lang="en">
   <head>
     <title>Vis Network | Edge Styles | Edge background</title>
 
diff --git a/examples/network/edgeStyles/colors.html b/examples/network/edgeStyles/colors.html
index 46c49c45e1..cdad8f3c63 100644
--- a/examples/network/edgeStyles/colors.html
+++ b/examples/network/edgeStyles/colors.html
@@ -1,5 +1,5 @@
 <!DOCTYPE html>
-<html>
+<html lang="en">
   <head>
     <title>Vis Network | Edge Styles | Colors</title>
 
diff --git a/examples/network/edgeStyles/dashes.html b/examples/network/edgeStyles/dashes.html
index d26aac42b1..0ef1163c31 100644
--- a/examples/network/edgeStyles/dashes.html
+++ b/examples/network/edgeStyles/dashes.html
@@ -1,5 +1,5 @@
 <!DOCTYPE html>
-<html>
+<html lang="en">
   <head>
     <title>Vis Network | Edge Styles | Dashes</title>
 
diff --git a/examples/network/edgeStyles/endPointOffsets.html b/examples/network/edgeStyles/endPointOffsets.html
index 7b9ded6e5f..7ad976d086 100644
--- a/examples/network/edgeStyles/endPointOffsets.html
+++ b/examples/network/edgeStyles/endPointOffsets.html
@@ -1,5 +1,5 @@
 <!DOCTYPE html>
-<html>
+<html lang="en">
   <head>
     <title>Vis Network | Edge Styles | Endpoint Offsets</title>
 
diff --git a/examples/network/edgeStyles/imageArrowHeads.html b/examples/network/edgeStyles/imageArrowHeads.html
index 69e97a9014..6f56ef526f 100644
--- a/examples/network/edgeStyles/imageArrowHeads.html
+++ b/examples/network/edgeStyles/imageArrowHeads.html
@@ -1,5 +1,5 @@
 <!DOCTYPE html>
-<html>
+<html lang="en">
   <head>
     <meta charset="utf-8" />
     <title>Vis Network | Edge Styles | Image Arrow Heads</title>
diff --git a/examples/network/edgeStyles/selfReference.html b/examples/network/edgeStyles/selfReference.html
index 28f00c730b..3f8f43987b 100644
--- a/examples/network/edgeStyles/selfReference.html
+++ b/examples/network/edgeStyles/selfReference.html
@@ -1,5 +1,5 @@
 <!DOCTYPE html>
-<html>
+<html lang="en">
   <head>
     <title>Vis Network | Edge Styles | Self Reference</title>
 
diff --git a/examples/network/edgeStyles/smooth.html b/examples/network/edgeStyles/smooth.html
index 09e88b840d..68469b16e2 100644
--- a/examples/network/edgeStyles/smooth.html
+++ b/examples/network/edgeStyles/smooth.html
@@ -1,5 +1,5 @@
 <!DOCTYPE html>
-<html>
+<html lang="en">
   <head>
     <title>Vis Network | Edge Styles | Static smooth curves</title>
 
diff --git a/examples/network/edgeStyles/smoothWorldCup.html b/examples/network/edgeStyles/smoothWorldCup.html
index 2923719c97..37d48c009e 100644
--- a/examples/network/edgeStyles/smoothWorldCup.html
+++ b/examples/network/edgeStyles/smoothWorldCup.html
@@ -1,6 +1,6 @@
 <!DOCTYPE html>
 <!-- saved from url=(0044)http://kenedict.com/networks/worldcup14/vis/ , thanks Andre!-->
-<html>
+<html lang="en">
   <head>
     <meta http-equiv="content-type" content="text/html; charset=UTF8" />
     <title>
diff --git a/examples/network/events/interactionEvents.html b/examples/network/events/interactionEvents.html
index 31d4481cbc..da260d38c2 100644
--- a/examples/network/events/interactionEvents.html
+++ b/examples/network/events/interactionEvents.html
@@ -1,5 +1,5 @@
 <!DOCTYPE html>
-<html>
+<html lang="en">
   <head>
     <title>Vis Network | Events | Interaction events</title>
 
diff --git a/examples/network/events/physicsEvents.html b/examples/network/events/physicsEvents.html
index da35e238a5..75343d1aac 100644
--- a/examples/network/events/physicsEvents.html
+++ b/examples/network/events/physicsEvents.html
@@ -1,5 +1,5 @@
 <!DOCTYPE html>
-<html>
+<html lang="en">
   <head>
     <title>Vis Network | Events | Physics Events</title>
 
diff --git a/examples/network/events/renderEvents.html b/examples/network/events/renderEvents.html
index 010da67c00..0d0e7c478b 100644
--- a/examples/network/events/renderEvents.html
+++ b/examples/network/events/renderEvents.html
@@ -1,5 +1,5 @@
 <!DOCTYPE html>
-<html>
+<html lang="en">
   <head>
     <title>Vis Network | Events | Rendering Events</title>
 
diff --git a/examples/network/exampleApplications/disassemblerExample.html b/examples/network/exampleApplications/disassemblerExample.html
index 7f39517ae2..cdb70b608f 100644
--- a/examples/network/exampleApplications/disassemblerExample.html
+++ b/examples/network/exampleApplications/disassemblerExample.html
@@ -1,4 +1,4 @@
-<html>
+<html lang="en">
   <head>
     <title>Vis Network | Example Applications | Disassembler</title>
     <style type="text/css">
diff --git a/examples/network/exampleApplications/lesMiserables.html b/examples/network/exampleApplications/lesMiserables.html
index 9153cafd72..530c4f5b6a 100644
--- a/examples/network/exampleApplications/lesMiserables.html
+++ b/examples/network/exampleApplications/lesMiserables.html
@@ -1,5 +1,5 @@
 <!DOCTYPE html>
-<html>
+<html lang="en">
   <head>
     <title>Vis Network | Example Applications | Les miserables</title>
 
diff --git a/examples/network/exampleApplications/loadingBar.html b/examples/network/exampleApplications/loadingBar.html
index 2e7f09ab84..2fc4310185 100644
--- a/examples/network/exampleApplications/loadingBar.html
+++ b/examples/network/exampleApplications/loadingBar.html
@@ -1,5 +1,5 @@
 <!DOCTYPE html>
-<html>
+<html lang="en">
   <head>
     <title>Vis Network | Example Applications | Loading Bar</title>
 
diff --git a/examples/network/exampleApplications/neighbourhoodHighlight.html b/examples/network/exampleApplications/neighbourhoodHighlight.html
index 0f89f890b8..e819f5c340 100644
--- a/examples/network/exampleApplications/neighbourhoodHighlight.html
+++ b/examples/network/exampleApplications/neighbourhoodHighlight.html
@@ -1,6 +1,6 @@
 <!DOCTYPE html>
 <!-- saved from url=(0044)http://kenedict.com/networks/worldcup14/vis/ , thanks Andre!-->
-<html>
+<html lang="en">
   <head>
     <meta http-equiv="content-type" content="text/html; charset=UTF8" />
     <title>
diff --git a/examples/network/exampleApplications/nodeLegend.html b/examples/network/exampleApplications/nodeLegend.html
index 2f8c52ee66..a3b904e682 100644
--- a/examples/network/exampleApplications/nodeLegend.html
+++ b/examples/network/exampleApplications/nodeLegend.html
@@ -1,6 +1,6 @@
 <!DOCTYPE html>
 <!-- saved from url=(0046)http://visjs.org/examples/network/03_images.html -->
-<html>
+<html lang="en">
   <head>
     <meta http-equiv="Content-Type" content="text/html; charset=ISO-8859-1" />
     <title>Vis Network | Example Applications | Node Legend</title>
diff --git a/examples/network/exampleApplications/worldCupPerformance.html b/examples/network/exampleApplications/worldCupPerformance.html
index 536d6594ea..a9f7b6996a 100644
--- a/examples/network/exampleApplications/worldCupPerformance.html
+++ b/examples/network/exampleApplications/worldCupPerformance.html
@@ -1,6 +1,6 @@
 <!DOCTYPE html>
 <!-- saved from url=(0044)http://kenedict.com/networks/worldcup14/vis/ , thanks Andre!-->
-<html>
+<html lang="en">
   <head>
     <meta http-equiv="content-type" content="text/html; charset=UTF8" />
     <title>Vis Network | Example Applications | World Cup Network</title>
diff --git a/examples/network/imageSelected/imageSelected.html b/examples/network/imageSelected/imageSelected.html
index 9ae7b7827b..bb95143869 100644
--- a/examples/network/imageSelected/imageSelected.html
+++ b/examples/network/imageSelected/imageSelected.html
@@ -1,4 +1,5 @@
-<html>
+<!DOCTYPE html>
+<html lang="en">
   <head>
     <title>Vis Network | Node Styles | Selected/Unselected Image</title>
 
diff --git a/examples/network/labels/labelAlignment.html b/examples/network/labels/labelAlignment.html
index 5515afe2df..fde387dad7 100644
--- a/examples/network/labels/labelAlignment.html
+++ b/examples/network/labels/labelAlignment.html
@@ -1,5 +1,5 @@
 <!DOCTYPE html>
-<html>
+<html lang="en">
   <head>
     <title>Vis Network | Labels | Label Alignment</title>
 
diff --git a/examples/network/labels/labelBackground.html b/examples/network/labels/labelBackground.html
index 43b838c462..b7e2810b29 100644
--- a/examples/network/labels/labelBackground.html
+++ b/examples/network/labels/labelBackground.html
@@ -1,5 +1,5 @@
 <!DOCTYPE html>
-<html>
+<html lang="en">
   <head>
     <title>Vis Network | Labels | Label Background</title>
 
diff --git a/examples/network/labels/labelColorAndSize.html b/examples/network/labels/labelColorAndSize.html
index a40da59084..9fe204bb1b 100644
--- a/examples/network/labels/labelColorAndSize.html
+++ b/examples/network/labels/labelColorAndSize.html
@@ -1,5 +1,5 @@
 <!DOCTYPE html>
-<html>
+<html lang="en">
   <head>
     <title>Vis Network | Labels | Label Color and Size</title>
 
diff --git a/examples/network/labels/labelMargins.html b/examples/network/labels/labelMargins.html
index 3fa81ef191..a7bcd30f9d 100644
--- a/examples/network/labels/labelMargins.html
+++ b/examples/network/labels/labelMargins.html
@@ -1,5 +1,5 @@
 <!DOCTYPE html>
-<html>
+<html lang="en">
   <head>
     <title>Vis Network | Labels | Label Margins</title>
 
diff --git a/examples/network/labels/labelMultifont.html b/examples/network/labels/labelMultifont.html
index 4597ba8b80..687cc4a2c8 100644
--- a/examples/network/labels/labelMultifont.html
+++ b/examples/network/labels/labelMultifont.html
@@ -1,5 +1,5 @@
 <!DOCTYPE html>
-<html>
+<html lang="en">
   <head>
     <title>Vis Network | Labels | Multifont Labels</title>
 
diff --git a/examples/network/labels/labelStroke.html b/examples/network/labels/labelStroke.html
index 1fd2bbcd7f..6039f549f1 100644
--- a/examples/network/labels/labelStroke.html
+++ b/examples/network/labels/labelStroke.html
@@ -1,5 +1,5 @@
 <!DOCTYPE html>
-<html>
+<html lang="en">
   <head>
     <title>Vis Network | Labels | Label stroke</title>
 
diff --git a/examples/network/labels/multilineText.html b/examples/network/labels/multilineText.html
index f7e9e2d2c1..425c6e2636 100644
--- a/examples/network/labels/multilineText.html
+++ b/examples/network/labels/multilineText.html
@@ -1,5 +1,5 @@
 <!DOCTYPE html>
-<html>
+<html lang="en">
   <head>
     <title>Vis Network | Labels | Multiline text</title>
 
diff --git a/examples/network/layout/hierarchicalLayout.html b/examples/network/layout/hierarchicalLayout.html
index 75dd496c91..50f7f5e815 100644
--- a/examples/network/layout/hierarchicalLayout.html
+++ b/examples/network/layout/hierarchicalLayout.html
@@ -1,5 +1,5 @@
 <!DOCTYPE html>
-<html>
+<html lang="en">
   <head>
     <title>Vis Network | Layouts | Hierarchical Layout</title>
 
diff --git a/examples/network/layout/hierarchicalLayoutBigUserDefined.html b/examples/network/layout/hierarchicalLayoutBigUserDefined.html
index 1e2f9e19d9..028f09707d 100644
--- a/examples/network/layout/hierarchicalLayoutBigUserDefined.html
+++ b/examples/network/layout/hierarchicalLayoutBigUserDefined.html
@@ -1,5 +1,5 @@
 <!DOCTYPE html>
-<html>
+<html lang="en">
   <head>
     <title>
       Vis Network | Layouts | User Defined Hierarchical Layout (Big)
diff --git a/examples/network/layout/hierarchicalLayoutDynamicChanges.html b/examples/network/layout/hierarchicalLayoutDynamicChanges.html
index f66dd99f2b..f3cd8e81b8 100644
--- a/examples/network/layout/hierarchicalLayoutDynamicChanges.html
+++ b/examples/network/layout/hierarchicalLayoutDynamicChanges.html
@@ -1,5 +1,5 @@
 <!DOCTYPE html>
-<html>
+<html lang="en">
   <head>
     <title>Vis Network | Layouts | Dynamic Hierarchical Layout Changes</title>
 
diff --git a/examples/network/layout/hierarchicalLayoutMethods.html b/examples/network/layout/hierarchicalLayoutMethods.html
index 981ed93851..9f782352b3 100644
--- a/examples/network/layout/hierarchicalLayoutMethods.html
+++ b/examples/network/layout/hierarchicalLayoutMethods.html
@@ -1,5 +1,5 @@
 <!DOCTYPE html>
-<html>
+<html lang="en">
   <head>
     <title>Vis Network | Layouts | Hierarchical Layout Methods</title>
 
diff --git a/examples/network/layout/hierarchicalLayoutOverlapAvoidance.html b/examples/network/layout/hierarchicalLayoutOverlapAvoidance.html
index 92eef49e5f..40a88383b2 100644
--- a/examples/network/layout/hierarchicalLayoutOverlapAvoidance.html
+++ b/examples/network/layout/hierarchicalLayoutOverlapAvoidance.html
@@ -1,5 +1,5 @@
 <!DOCTYPE html>
-<html>
+<html lang="en">
   <head>
     <title>Vis Network | Layouts | Hierarchical Layout Overlap Avoidance</title>
 
diff --git a/examples/network/layout/hierarchicalLayoutUserdefined.html b/examples/network/layout/hierarchicalLayoutUserdefined.html
index 2dac7815cf..87581e28ea 100644
--- a/examples/network/layout/hierarchicalLayoutUserdefined.html
+++ b/examples/network/layout/hierarchicalLayoutUserdefined.html
@@ -1,5 +1,5 @@
 <!DOCTYPE html>
-<html>
+<html lang="en">
   <head>
     <title>
       Vis Network | Layouts | User Defined Hierarchical Layout (Configurable)
diff --git a/examples/network/layout/hierarchicalLayoutWithoutPhysics.html b/examples/network/layout/hierarchicalLayoutWithoutPhysics.html
index baa275d5b8..822c7783a1 100644
--- a/examples/network/layout/hierarchicalLayoutWithoutPhysics.html
+++ b/examples/network/layout/hierarchicalLayoutWithoutPhysics.html
@@ -1,4 +1,4 @@
-<html>
+<html lang="en">
   <head>
     <meta charset="utf-8" />
     <title>Vis Network | Layouts | Hierarchical Layout without Physics</title>
diff --git a/examples/network/layout/randomSeed.html b/examples/network/layout/randomSeed.html
index 05cb1f2f26..59db41da33 100644
--- a/examples/network/layout/randomSeed.html
+++ b/examples/network/layout/randomSeed.html
@@ -1,5 +1,5 @@
 <!DOCTYPE html>
-<html>
+<html lang="en">
   <head>
     <title>Vis Network | Layouts | Setting the Random Seed</title>
 
diff --git a/examples/network/nodeStyles/HTMLInNodes.html b/examples/network/nodeStyles/HTMLInNodes.html
index 77b4aa3a05..e81f99761d 100644
--- a/examples/network/nodeStyles/HTMLInNodes.html
+++ b/examples/network/nodeStyles/HTMLInNodes.html
@@ -1,5 +1,5 @@
 <!DOCTYPE html>
-<html>
+<html lang="en">
   <head>
     <title>Vis Network | Node Styles | HTML in Nodes</title>
 
diff --git a/examples/network/nodeStyles/circularImages.html b/examples/network/nodeStyles/circularImages.html
index 0b8fd474fe..dcbeac438e 100644
--- a/examples/network/nodeStyles/circularImages.html
+++ b/examples/network/nodeStyles/circularImages.html
@@ -1,5 +1,5 @@
 <!DOCTYPE html>
-<html>
+<html lang="en">
   <head>
     <title>Vis Network | Node Styles | Circular Images</title>
 
diff --git a/examples/network/nodeStyles/colors.html b/examples/network/nodeStyles/colors.html
index afccdc85ba..6f8949743f 100644
--- a/examples/network/nodeStyles/colors.html
+++ b/examples/network/nodeStyles/colors.html
@@ -1,5 +1,5 @@
 <!DOCTYPE html>
-<html>
+<html lang="en">
   <head>
     <title>Vis Network | Node Styles | Colors</title>
 
diff --git a/examples/network/nodeStyles/customGroups.html b/examples/network/nodeStyles/customGroups.html
index 32dd95eca0..f270ed8d43 100644
--- a/examples/network/nodeStyles/customGroups.html
+++ b/examples/network/nodeStyles/customGroups.html
@@ -1,5 +1,5 @@
 <!DOCTYPE html>
-<html>
+<html lang="en">
   <head>
     <title>Vis Network | Node Styles | Custom Groups</title>
 
diff --git a/examples/network/nodeStyles/groups.html b/examples/network/nodeStyles/groups.html
index 9b97a96483..09900ab653 100644
--- a/examples/network/nodeStyles/groups.html
+++ b/examples/network/nodeStyles/groups.html
@@ -1,5 +1,5 @@
 <!DOCTYPE html>
-<html>
+<html lang="en">
   <head>
     <title>Vis Network | Node Styles | Groups</title>
 
diff --git a/examples/network/nodeStyles/images.html b/examples/network/nodeStyles/images.html
index 00a349ec79..900bc2616c 100644
--- a/examples/network/nodeStyles/images.html
+++ b/examples/network/nodeStyles/images.html
@@ -1,5 +1,5 @@
 <!DOCTYPE html>
-<html>
+<html lang="en">
   <head>
     <title>Vis Network | Node Styles | Images</title>
 
diff --git a/examples/network/nodeStyles/imagesWithBorders.html b/examples/network/nodeStyles/imagesWithBorders.html
index 1709d3bec5..ef7869ac99 100644
--- a/examples/network/nodeStyles/imagesWithBorders.html
+++ b/examples/network/nodeStyles/imagesWithBorders.html
@@ -1,5 +1,5 @@
 <!DOCTYPE html>
-<html>
+<html lang="en">
   <head>
     <title>Vis Network | Node Styles | Images with Borders</title>
 
diff --git a/examples/network/nodeStyles/imagesWithBordersAndPadding.html b/examples/network/nodeStyles/imagesWithBordersAndPadding.html
index 7e65148d46..4fe1500110 100644
--- a/examples/network/nodeStyles/imagesWithBordersAndPadding.html
+++ b/examples/network/nodeStyles/imagesWithBordersAndPadding.html
@@ -1,5 +1,5 @@
 <!DOCTYPE html>
-<html>
+<html lang="en">
   <head>
     <title>
       Vis Network | Node Styles | Images with Borders and Image Padding
diff --git a/examples/network/nodeStyles/imagesWithCoordinateOrigin.html b/examples/network/nodeStyles/imagesWithCoordinateOrigin.html
index a3ac171173..68f6d7aad2 100644
--- a/examples/network/nodeStyles/imagesWithCoordinateOrigin.html
+++ b/examples/network/nodeStyles/imagesWithCoordinateOrigin.html
@@ -1,5 +1,5 @@
 <!DOCTYPE html>
-<html>
+<html lang="en">
   <head>
     <title>
       Vis Network | Node Styles | Images with alternative coordinate origin
diff --git a/examples/network/nodeStyles/imagesWithOpacity.html b/examples/network/nodeStyles/imagesWithOpacity.html
index f9f0510483..81266fa0f3 100644
--- a/examples/network/nodeStyles/imagesWithOpacity.html
+++ b/examples/network/nodeStyles/imagesWithOpacity.html
@@ -1,5 +1,5 @@
 <!DOCTYPE html>
-<html>
+<html lang="en">
   <head>
     <title>Vis Network | Node Styles | Images with Opacity</title>
 
diff --git a/examples/network/nodeStyles/overwriteGroups.html b/examples/network/nodeStyles/overwriteGroups.html
index 458fc11c3c..4d714672f9 100644
--- a/examples/network/nodeStyles/overwriteGroups.html
+++ b/examples/network/nodeStyles/overwriteGroups.html
@@ -1,5 +1,5 @@
 <!DOCTYPE html>
-<html>
+<html lang="en">
   <head>
     <title>Vis Network | Node Styles | Overriding Group Styles</title>
 
diff --git a/examples/network/nodeStyles/shadows.html b/examples/network/nodeStyles/shadows.html
index 2721203b36..ac1378f3b2 100644
--- a/examples/network/nodeStyles/shadows.html
+++ b/examples/network/nodeStyles/shadows.html
@@ -1,5 +1,5 @@
 <!DOCTYPE html>
-<html>
+<html lang="en">
   <head>
     <title>Vis Network | Node Styles | Shadows</title>
 
diff --git a/examples/network/nodeStyles/shapes.html b/examples/network/nodeStyles/shapes.html
index db7785c160..d6559c3e2c 100644
--- a/examples/network/nodeStyles/shapes.html
+++ b/examples/network/nodeStyles/shapes.html
@@ -1,5 +1,5 @@
 <!DOCTYPE html>
-<html>
+<html lang="en">
   <head>
     <title>Vis Network | Node Styles | Shapes</title>
 
diff --git a/examples/network/nodeStyles/shapesWithDashedBorders.html b/examples/network/nodeStyles/shapesWithDashedBorders.html
index 9cd4a4d9f4..aa92f2d5a5 100644
--- a/examples/network/nodeStyles/shapesWithDashedBorders.html
+++ b/examples/network/nodeStyles/shapesWithDashedBorders.html
@@ -1,5 +1,5 @@
 <!DOCTYPE html>
-<html>
+<html lang="en">
   <head>
     <title>Vis Network | Node Styles | Shapes with Dashed Borders</title>
 
diff --git a/examples/network/nodeStyles/widthHeight.html b/examples/network/nodeStyles/widthHeight.html
index be40c9de63..1d3f2d12d6 100644
--- a/examples/network/nodeStyles/widthHeight.html
+++ b/examples/network/nodeStyles/widthHeight.html
@@ -1,5 +1,5 @@
 <!DOCTYPE html>
-<html>
+<html lang="en">
   <head>
     <title>Vis Network | Node Styles | Label Width and Height Settings</title>
 
diff --git a/examples/network/other/animationShowcase.html b/examples/network/other/animationShowcase.html
index 7386bdbae1..2f65cc5c5f 100644
--- a/examples/network/other/animationShowcase.html
+++ b/examples/network/other/animationShowcase.html
@@ -1,5 +1,5 @@
 <!DOCTYPE html>
-<html>
+<html lang="en">
   <head>
     <title>Vis Network | Other | Animations</title>
 
diff --git a/examples/network/other/automaticResizing.html b/examples/network/other/automaticResizing.html
index 17b9ff8699..cfbe47946a 100644
--- a/examples/network/other/automaticResizing.html
+++ b/examples/network/other/automaticResizing.html
@@ -1,5 +1,5 @@
 <!DOCTYPE html>
-<html>
+<html lang="en">
   <head>
     <title>Vis Network | Other | Automatic Resizing</title>
 
diff --git a/examples/network/other/changingClusteredEdgesNodes.html b/examples/network/other/changingClusteredEdgesNodes.html
index c01966192b..4442948780 100644
--- a/examples/network/other/changingClusteredEdgesNodes.html
+++ b/examples/network/other/changingClusteredEdgesNodes.html
@@ -1,5 +1,5 @@
 <!DOCTYPE html>
-<html>
+<html lang="en">
   <head>
     <title>Vis Network | Other | Changing Clustered Edges and Nodes</title>
 
diff --git a/examples/network/other/chosen.html b/examples/network/other/chosen.html
index 09b27b6807..54df7b80a1 100644
--- a/examples/network/other/chosen.html
+++ b/examples/network/other/chosen.html
@@ -1,5 +1,5 @@
 <!DOCTYPE html>
-<html>
+<html lang="en">
   <head>
     <title>Vis Network | Other | Chosen Elements</title>
 
diff --git a/examples/network/other/clustering.html b/examples/network/other/clustering.html
index a23761af3f..7d8a97b9aa 100644
--- a/examples/network/other/clustering.html
+++ b/examples/network/other/clustering.html
@@ -1,5 +1,5 @@
 <!DOCTYPE html>
-<html>
+<html lang="en">
   <head>
     <title>Vis Network | Other | Clustering</title>
 
diff --git a/examples/network/other/clusteringByZoom.html b/examples/network/other/clusteringByZoom.html
index 3ea337a443..176df679f3 100644
--- a/examples/network/other/clusteringByZoom.html
+++ b/examples/network/other/clusteringByZoom.html
@@ -1,5 +1,5 @@
 <!DOCTYPE html>
-<html>
+<html lang="en">
   <head>
     <title>Vis Network | Other | Clustering by Zoom Level</title>
 
diff --git a/examples/network/other/configuration.html b/examples/network/other/configuration.html
index 39165fffad..def2813fc8 100644
--- a/examples/network/other/configuration.html
+++ b/examples/network/other/configuration.html
@@ -1,5 +1,5 @@
 <!DOCTYPE html>
-<html>
+<html lang="en">
   <head>
     <title>Vis Network | Other | Playing with Physics</title>
 
diff --git a/examples/network/other/cursorChange.html b/examples/network/other/cursorChange.html
index 6005f449bd..7b58e338cb 100644
--- a/examples/network/other/cursorChange.html
+++ b/examples/network/other/cursorChange.html
@@ -1,5 +1,5 @@
 <!DOCTYPE html>
-<html>
+<html lang="en">
   <head>
     <title>Vis Network | Other | Cursor Change</title>
 
@@ -77,7 +77,7 @@
       &nbsp;
 
       <button
-        onClick="changeEventCursor(document.getElementById('eventType').value,document.getElementById('cursorType').value);"
+        onclick="changeEventCursor(document.getElementById('eventType').value,document.getElementById('cursorType').value);"
       >
         Change Cursor for Event
       </button>
diff --git a/examples/network/other/manipulation.html b/examples/network/other/manipulation.html
index 9c3de5feb5..86ce3e6e4f 100644
--- a/examples/network/other/manipulation.html
+++ b/examples/network/other/manipulation.html
@@ -1,5 +1,5 @@
 <!DOCTYPE html>
-<html>
+<html lang="en">
   <head>
     <meta charset="utf-8" />
     <title>Vis Network | Manipulation | Manipulation with Localization</title>
@@ -104,6 +104,7 @@
         var options = {
           layout: { randomSeed: seed }, // just to make sure the layout is the same when the locale is changed
           locale: document.getElementById("locale").value,
+          interaction: { keyboard: true },
           manipulation: {
             addNode: function (data, callback) {
               // filling in the popup DOM elements
diff --git a/examples/network/other/manipulationEditEdgeNoDrag.html b/examples/network/other/manipulationEditEdgeNoDrag.html
index d60db34dd3..a2218aa41e 100644
--- a/examples/network/other/manipulationEditEdgeNoDrag.html
+++ b/examples/network/other/manipulationEditEdgeNoDrag.html
@@ -1,5 +1,5 @@
 <!DOCTYPE html>
-<html>
+<html lang="en">
   <head>
     <meta charset="utf-8" />
     <title>Vis Network | Manipulation | Edit Edge Without Drag</title>
diff --git a/examples/network/other/navigation.html b/examples/network/other/navigation.html
index 0048c54967..21155913f5 100644
--- a/examples/network/other/navigation.html
+++ b/examples/network/other/navigation.html
@@ -1,5 +1,5 @@
 <!DOCTYPE html>
-<html>
+<html lang="en">
   <head>
     <title>Vis Network | Other | Navigation</title>
 
diff --git a/examples/network/other/onLoadAnimation.html b/examples/network/other/onLoadAnimation.html
index 6f7e0fe4b5..c398a536c9 100644
--- a/examples/network/other/onLoadAnimation.html
+++ b/examples/network/other/onLoadAnimation.html
@@ -1,4 +1,4 @@
-<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
+<!DOCTYPE html>
 <html xmlns="http://www.w3.org/1999/xhtml">
   <head>
     <title>Vis Network | Other | On Load Animation</title>
@@ -42,7 +42,7 @@ <h2>Vis.js network onLoad animation</h2>
         <option value="easeInOutQuint">easeInOutQuint</option>
       </select>
       <button
-        onClick="createNetwork(document.getElementById('easingFunction').value);"
+        onclick="createNetwork(document.getElementById('easingFunction').value);"
       >
         Demo Easing Function
       </button>
diff --git a/examples/network/other/performance.html b/examples/network/other/performance.html
index 57e05eb4dc..6b9a0c1253 100644
--- a/examples/network/other/performance.html
+++ b/examples/network/other/performance.html
@@ -1,5 +1,5 @@
 <!DOCTYPE html>
-<html>
+<html lang="en">
   <head>
     <title>Vis Network | Other | Performance</title>
 
diff --git a/examples/network/other/saveAndLoad.html b/examples/network/other/saveAndLoad.html
index dfdcf9f52f..faf40f5d17 100644
--- a/examples/network/other/saveAndLoad.html
+++ b/examples/network/other/saveAndLoad.html
@@ -1,5 +1,5 @@
 <!DOCTYPE html>
-<html>
+<html lang="en">
   <head>
     <meta content="text/html;charset=utf-8" http-equiv="Content-Type" />
     <meta content="utf-8" http-equiv="encoding" />
diff --git a/examples/network/physics/physicsConfiguration.html b/examples/network/physics/physicsConfiguration.html
index add8ebed2a..1455f1974c 100644
--- a/examples/network/physics/physicsConfiguration.html
+++ b/examples/network/physics/physicsConfiguration.html
@@ -1,5 +1,5 @@
 <!DOCTYPE html>
-<html>
+<html lang="en">
   <head>
     <title>Vis Network | Physics | Playing with Physics</title>
 
diff --git a/examples/network/physics/wind.html b/examples/network/physics/wind.html
index 92ed12ec22..f930966f58 100644
--- a/examples/network/physics/wind.html
+++ b/examples/network/physics/wind.html
@@ -1,5 +1,5 @@
 <!DOCTYPE html>
-<html>
+<html lang="en">
   <head>
     <title>Vis Network | Physics | Wind</title>
 
diff --git a/examples/network/tests/hidden_edge_test.html b/examples/network/tests/hidden_edge_test.html
index e80c5cbea4..5b68941bb4 100644
--- a/examples/network/tests/hidden_edge_test.html
+++ b/examples/network/tests/hidden_edge_test.html
@@ -1,5 +1,5 @@
 <!DOCTYPE html>
-<html>
+<html lang="en">
   <head>
     <meta charset="utf-8" />
     <title>Vis Network | Tests | Hidden Edge Test</title>
diff --git a/examples/network/version_migration/5.4.1_to_6.0.0/manipulationEditEdgeNoDrag.html b/examples/network/version_migration/5.4.1_to_6.0.0/manipulationEditEdgeNoDrag.html
index fc62115ef4..769965131d 100644
--- a/examples/network/version_migration/5.4.1_to_6.0.0/manipulationEditEdgeNoDrag.html
+++ b/examples/network/version_migration/5.4.1_to_6.0.0/manipulationEditEdgeNoDrag.html
@@ -1,5 +1,5 @@
 <!DOCTYPE html>
-<html>
+<html lang="en">
   <head>
     <meta charset="utf-8" />
     <title>
diff --git a/index.html b/index.html
index 3c048c6626..641a09d2bd 100644
--- a/index.html
+++ b/index.html
@@ -1,5 +1,5 @@
 <!DOCTYPE html>
-<html>
+<html lang="en">
   <head>
     <meta charset="utf-8" />
     <title>Vis Network</title>
diff --git a/lib/network/locales.ts b/lib/network/locales.ts
index eabffe7c78..d4873da7c1 100644
--- a/lib/network/locales.ts
+++ b/lib/network/locales.ts
@@ -3,6 +3,7 @@ export interface Locale {
   addEdge: string;
   addNode: string;
   back: string;
+  close: string;
   createEdgeError: string;
   del: string;
   deleteClusterError: string;
@@ -21,6 +22,7 @@ export const en: Locale = {
   addEdge: "Add Edge",
   addNode: "Add Node",
   back: "Back",
+  close: "Close",
   createEdgeError: "Cannot link edges to a cluster.",
   del: "Delete selected",
   deleteClusterError: "Clusters cannot be deleted.",
@@ -41,6 +43,7 @@ export const de: Locale = {
   addEdge: "Kante hinzuf\u00fcgen",
   addNode: "Knoten hinzuf\u00fcgen",
   back: "Zur\u00fcck",
+  close: "Schließen",
   createEdgeError:
     "Es ist nicht m\u00f6glich, Kanten mit Clustern zu verbinden.",
   del: "L\u00f6sche Auswahl",
@@ -62,6 +65,7 @@ export const es: Locale = {
   addEdge: "A\u00f1adir arista",
   addNode: "A\u00f1adir nodo",
   back: "Atr\u00e1s",
+  close: "Cerrar",
   createEdgeError: "No se puede conectar una arista a un grupo.",
   del: "Eliminar selecci\u00f3n",
   deleteClusterError: "No es posible eliminar grupos.",
@@ -81,6 +85,7 @@ export const it: Locale = {
   addEdge: "Aggiungi un vertice",
   addNode: "Aggiungi un nodo",
   back: "Indietro",
+  close: "Chiudere",
   createEdgeError: "Non si possono collegare vertici ad un cluster",
   del: "Cancella la selezione",
   deleteClusterError: "I cluster non possono essere cancellati",
@@ -100,6 +105,7 @@ export const nl: Locale = {
   addEdge: "Link toevoegen",
   addNode: "Node toevoegen",
   back: "Terug",
+  close: "Sluiten",
   createEdgeError: "Kan geen link maken naar een cluster.",
   del: "Selectie verwijderen",
   deleteClusterError: "Clusters kunnen niet worden verwijderd.",
@@ -119,6 +125,7 @@ export const pt: Locale = {
   addEdge: "Adicionar aresta",
   addNode: "Adicionar nó",
   back: "Voltar",
+  close: "Fechar",
   createEdgeError: "Não foi possível linkar arestas a um cluster.",
   del: "Remover selecionado",
   deleteClusterError: "Clusters não puderam ser removidos.",
@@ -138,6 +145,7 @@ export const ru: Locale = {
   addEdge: "Добавить ребро",
   addNode: "Добавить узел",
   back: "Назад",
+  close: "Закрывать",
   createEdgeError: "Невозможно соединить ребра в кластер.",
   del: "Удалить выбранное",
   deleteClusterError: "Кластеры не могут быть удалены",
@@ -157,6 +165,7 @@ export const cn: Locale = {
   addEdge: "添加连接线",
   addNode: "添加节点",
   back: "返回",
+  close: "關閉",
   createEdgeError: "无法将连接线连接到群集。",
   del: "删除选定",
   deleteClusterError: "无法删除群集。",
@@ -174,6 +183,7 @@ export const uk: Locale = {
   addEdge: "Додати край",
   addNode: "Додати вузол",
   back: "Назад",
+  close: "Закрити",
   createEdgeError: "Не можливо об'єднати краї в групу.",
   del: "Видалити обране",
   deleteClusterError: "Групи не можуть бути видалені.",
@@ -193,6 +203,7 @@ export const fr: Locale = {
   addEdge: "Ajouter un lien",
   addNode: "Ajouter un nœud",
   back: "Retour",
+  close: "Fermer",
   createEdgeError: "Impossible de créer un lien vers un cluster.",
   del: "Effacer la sélection",
   deleteClusterError: "Les clusters ne peuvent pas être effacés.",
@@ -212,6 +223,7 @@ export const cs: Locale = {
   addEdge: "Přidat hranu",
   addNode: "Přidat vrchol",
   back: "Zpět",
+  close: "Zavřít",
   createEdgeError: "Nelze připojit hranu ke shluku.",
   del: "Smazat výběr",
   deleteClusterError: "Nelze mazat shluky.",
diff --git a/lib/network/modules/Canvas.js b/lib/network/modules/Canvas.js
index 10ff6bf091..657709dda5 100644
--- a/lib/network/modules/Canvas.js
+++ b/lib/network/modules/Canvas.js
@@ -232,7 +232,7 @@ class Canvas {
     this.frame.className = "vis-network";
     this.frame.style.position = "relative";
     this.frame.style.overflow = "hidden";
-    this.frame.tabIndex = 900; // tab index is required for keycharm to bind keystrokes to the div instead of the window
+    this.frame.tabIndex = 0; // tab index is required for keycharm to bind keystrokes to the div instead of the window
 
     //////////////////////////////////////////////////////////////////
 
diff --git a/lib/network/modules/ManipulationSystem.css b/lib/network/modules/ManipulationSystem.css
index 93b2516e15..b1f27fafaf 100644
--- a/lib/network/modules/ManipulationSystem.css
+++ b/lib/network/modules/ManipulationSystem.css
@@ -60,7 +60,8 @@ div.vis-network div.vis-manipulation {
   height: 28px;
 }
 
-div.vis-network div.vis-edit-mode {
+div.vis-network div.vis-edit-mode,
+div.vis-network button.vis-edit-mode {
   position: absolute;
   left: 0;
   top: 5px;
@@ -69,16 +70,18 @@ div.vis-network div.vis-edit-mode {
 
 /* FIXME: shouldn't the vis-close button be a child of the vis-manipulation div? */
 
-div.vis-network div.vis-close {
+div.vis-network button.vis-close {
   position: absolute;
   right: 0;
   top: 0;
   width: 30px;
   height: 30px;
 
+  background-color: transparent;
   background-position: 20px 3px;
   background-repeat: no-repeat;
   background-image: inline("cross.png");
+  border: none;
   cursor: pointer;
   -webkit-touch-callout: none;
   -webkit-user-select: none;
@@ -88,23 +91,24 @@ div.vis-network div.vis-close {
   user-select: none;
 }
 
-div.vis-network div.vis-close:hover {
+div.vis-network button.vis-close:hover {
   opacity: 0.6;
 }
 
-div.vis-network div.vis-manipulation div.vis-button,
-div.vis-network div.vis-edit-mode div.vis-button {
+div.vis-network div.vis-manipulation button.vis-button,
+div.vis-network div.vis-edit-mode button.vis-button {
   float: left;
   font-family: verdana;
   font-size: 12px;
+  border: none;
+  box-sizing: content-box;
   -moz-border-radius: 15px;
   border-radius: 15px;
-  display: inline-block;
+  background-color: transparent;
   background-position: 0px 0px;
   background-repeat: no-repeat;
   height: 24px;
   margin-left: 10px;
-  /*vertical-align:middle;*/
   cursor: pointer;
   padding: 0px 8px 0px 8px;
   -webkit-touch-callout: none;
@@ -115,52 +119,53 @@ div.vis-network div.vis-edit-mode div.vis-button {
   user-select: none;
 }
 
-div.vis-network div.vis-manipulation div.vis-button:hover {
+div.vis-network div.vis-manipulation button.vis-button:hover {
   box-shadow: 1px 1px 8px rgba(0, 0, 0, 0.2);
 }
 
-div.vis-network div.vis-manipulation div.vis-button:active {
+div.vis-network div.vis-manipulation button.vis-button:active {
   box-shadow: 1px 1px 8px rgba(0, 0, 0, 0.5);
 }
 
-div.vis-network div.vis-manipulation div.vis-button.vis-back {
+div.vis-network div.vis-manipulation button.vis-button.vis-back {
   background-image: inline("backIcon.png");
 }
 
-div.vis-network div.vis-manipulation div.vis-button.vis-none:hover {
+div.vis-network div.vis-manipulation div.vis-none:hover {
   box-shadow: 1px 1px 8px rgba(0, 0, 0, 0);
   cursor: default;
 }
-div.vis-network div.vis-manipulation div.vis-button.vis-none:active {
+div.vis-network div.vis-manipulation div.vis-none:active {
   box-shadow: 1px 1px 8px rgba(0, 0, 0, 0);
 }
-div.vis-network div.vis-manipulation div.vis-button.vis-none {
-  padding: 0;
+div.vis-network div.vis-manipulation div.vis-none {
+  padding: 0px;
+  line-height: 23px;
 }
 div.vis-network div.vis-manipulation div.notification {
   margin: 2px;
   font-weight: bold;
 }
 
-div.vis-network div.vis-manipulation div.vis-button.vis-add {
+div.vis-network div.vis-manipulation button.vis-button.vis-add {
   background-image: inline("addNodeIcon.png");
 }
 
-div.vis-network div.vis-manipulation div.vis-button.vis-edit,
-div.vis-network div.vis-edit-mode div.vis-button.vis-edit {
+div.vis-network div.vis-manipulation button.vis-button.vis-edit,
+div.vis-network div.vis-edit-mode button.vis-button.vis-edit {
   background-image: inline("editIcon.png");
 }
 
-div.vis-network div.vis-edit-mode div.vis-button.vis-edit.vis-edit-mode {
+div.vis-network div.vis-edit-mode button.vis-button.vis-edit.vis-edit-mode {
   background-color: #fcfcfc;
   border: 1px solid #cccccc;
 }
 
-div.vis-network div.vis-manipulation div.vis-button.vis-connect {
+div.vis-network div.vis-manipulation button.vis-button.vis-connect {
   background-image: inline("connectIcon.png");
 }
 
-div.vis-network div.vis-manipulation div.vis-button.vis-delete {
+div.vis-network div.vis-manipulation button.vis-button.vis-delete {
   background-image: inline("deleteIcon.png");
 }
 /* top right bottom left */
diff --git a/lib/network/modules/ManipulationSystem.js b/lib/network/modules/ManipulationSystem.js
index 5fe51e6c2e..9e63758b23 100644
--- a/lib/network/modules/ManipulationSystem.js
+++ b/lib/network/modules/ManipulationSystem.js
@@ -28,7 +28,7 @@ class ManipulationSystem {
     this.editModeDiv = undefined;
     this.closeDiv = undefined;
 
-    this.manipulationHammers = [];
+    this._domEventListenerCleanupQueue = [];
     this.temporaryUIFunctions = {};
     this.temporaryEventFunctions = [];
 
@@ -242,7 +242,7 @@ class ManipulationSystem {
       }
 
       // bind the close button
-      this._bindHammerToDiv(this.closeDiv, this.toggleEditMode.bind(this));
+      this._bindElementEvents(this.closeDiv, this.toggleEditMode.bind(this));
 
       // refresh this bar based on what has been selected
       this._temporaryBindEvent(
@@ -278,7 +278,7 @@ class ManipulationSystem {
       );
 
       // bind the close button
-      this._bindHammerToDiv(this.closeDiv, this.toggleEditMode.bind(this));
+      this._bindElementEvents(this.closeDiv, this.toggleEditMode.bind(this));
     }
 
     this._temporaryBindEvent("click", this._performAddNode.bind(this));
@@ -361,7 +361,7 @@ class ManipulationSystem {
       );
 
       // bind the close button
-      this._bindHammerToDiv(this.closeDiv, this.toggleEditMode.bind(this));
+      this._bindElementEvents(this.closeDiv, this.toggleEditMode.bind(this));
     }
 
     // temporarily overload functions
@@ -408,7 +408,7 @@ class ManipulationSystem {
       );
 
       // bind the close button
-      this._bindHammerToDiv(this.closeDiv, this.toggleEditMode.bind(this));
+      this._bindElementEvents(this.closeDiv, this.toggleEditMode.bind(this));
     }
 
     this.edgeBeingEditedId = this.selectionHandler.getSelectedEdgeIds()[0];
@@ -585,8 +585,13 @@ class ManipulationSystem {
 
     // container for the close div button
     if (this.closeDiv === undefined) {
-      this.closeDiv = document.createElement("div");
+      this.closeDiv = document.createElement("button");
       this.closeDiv.className = "vis-close";
+      this.closeDiv.setAttribute(
+        "aria-label",
+        this.options.locales[this.options.locale]?.["close"] ??
+          this.options.locales["en"]["close"]
+      );
       this.closeDiv.style.display = this.manipulationDiv.style.display;
       this.canvas.frame.appendChild(this.closeDiv);
     }
@@ -633,13 +638,13 @@ class ManipulationSystem {
     const locale = this.options.locales[this.options.locale];
     const button = this._createButton(
       "editMode",
-      "vis-button vis-edit vis-edit-mode",
+      "vis-edit vis-edit-mode",
       locale["edit"] || this.options.locales["en"]["edit"]
     );
     this.editModeDiv.appendChild(button);
 
     // bind a hammer listener to the button, calling the function toggleEditMode.
-    this._bindHammerToDiv(button, this.toggleEditMode.bind(this));
+    this._bindElementEvents(button, this.toggleEditMode.bind(this));
   }
 
   /**
@@ -657,7 +662,7 @@ class ManipulationSystem {
       recursiveDOMDelete(this.manipulationDiv);
 
       // removes all the bindings and overloads
-      this._cleanManipulatorHammers();
+      this._cleanupDOMEventListeners();
     }
 
     // remove temporary nodes and edges
@@ -678,13 +683,10 @@ class ManipulationSystem {
    *
    * @private
    */
-  _cleanManipulatorHammers() {
-    // _clean hammer bindings
-    if (this.manipulationHammers.length != 0) {
-      for (let i = 0; i < this.manipulationHammers.length; i++) {
-        this.manipulationHammers[i].destroy();
-      }
-      this.manipulationHammers = [];
+  _cleanupDOMEventListeners() {
+    // _clean DOM event listener bindings
+    for (const callback of this._domEventListenerCleanupQueue.splice(0)) {
+      callback();
     }
   }
 
@@ -746,11 +748,11 @@ class ManipulationSystem {
   _createAddNodeButton(locale) {
     const button = this._createButton(
       "addNode",
-      "vis-button vis-add",
+      "vis-add",
       locale["addNode"] || this.options.locales["en"]["addNode"]
     );
     this.manipulationDiv.appendChild(button);
-    this._bindHammerToDiv(button, this.addNodeMode.bind(this));
+    this._bindElementEvents(button, this.addNodeMode.bind(this));
   }
 
   /**
@@ -761,11 +763,11 @@ class ManipulationSystem {
   _createAddEdgeButton(locale) {
     const button = this._createButton(
       "addEdge",
-      "vis-button vis-connect",
+      "vis-connect",
       locale["addEdge"] || this.options.locales["en"]["addEdge"]
     );
     this.manipulationDiv.appendChild(button);
-    this._bindHammerToDiv(button, this.addEdgeMode.bind(this));
+    this._bindElementEvents(button, this.addEdgeMode.bind(this));
   }
 
   /**
@@ -776,11 +778,11 @@ class ManipulationSystem {
   _createEditNodeButton(locale) {
     const button = this._createButton(
       "editNode",
-      "vis-button vis-edit",
+      "vis-edit",
       locale["editNode"] || this.options.locales["en"]["editNode"]
     );
     this.manipulationDiv.appendChild(button);
-    this._bindHammerToDiv(button, this.editNode.bind(this));
+    this._bindElementEvents(button, this.editNode.bind(this));
   }
 
   /**
@@ -791,11 +793,11 @@ class ManipulationSystem {
   _createEditEdgeButton(locale) {
     const button = this._createButton(
       "editEdge",
-      "vis-button vis-edit",
+      "vis-edit",
       locale["editEdge"] || this.options.locales["en"]["editEdge"]
     );
     this.manipulationDiv.appendChild(button);
-    this._bindHammerToDiv(button, this.editEdgeMode.bind(this));
+    this._bindElementEvents(button, this.editEdgeMode.bind(this));
   }
 
   /**
@@ -806,9 +808,9 @@ class ManipulationSystem {
   _createDeleteButton(locale) {
     let deleteBtnClass;
     if (this.options.rtl) {
-      deleteBtnClass = "vis-button vis-delete-rtl";
+      deleteBtnClass = "vis-delete-rtl";
     } else {
-      deleteBtnClass = "vis-button vis-delete";
+      deleteBtnClass = "vis-delete";
     }
     const button = this._createButton(
       "delete",
@@ -816,7 +818,7 @@ class ManipulationSystem {
       locale["del"] || this.options.locales["en"]["del"]
     );
     this.manipulationDiv.appendChild(button);
-    this._bindHammerToDiv(button, this.deleteSelected.bind(this));
+    this._bindElementEvents(button, this.deleteSelected.bind(this));
   }
 
   /**
@@ -827,11 +829,11 @@ class ManipulationSystem {
   _createBackButton(locale) {
     const button = this._createButton(
       "back",
-      "vis-button vis-back",
+      "vis-back",
       locale["back"] || this.options.locales["en"]["back"]
     );
     this.manipulationDiv.appendChild(button);
-    this._bindHammerToDiv(button, this.showManipulatorToolbar.bind(this));
+    this._bindElementEvents(button, this.showManipulatorToolbar.bind(this));
   }
 
   /**
@@ -844,8 +846,8 @@ class ManipulationSystem {
    * @private
    */
   _createButton(id, className, label, labelClassName = "vis-label") {
-    this.manipulationDOM[id + "Div"] = document.createElement("div");
-    this.manipulationDOM[id + "Div"].className = className;
+    this.manipulationDOM[id + "Div"] = document.createElement("button");
+    this.manipulationDOM[id + "Div"].className = "vis-button " + className;
     this.manipulationDOM[id + "Label"] = document.createElement("div");
     this.manipulationDOM[id + "Label"].className = labelClassName;
     this.manipulationDOM[id + "Label"].innerHTML = label;
@@ -861,9 +863,10 @@ class ManipulationSystem {
    * @private
    */
   _createDescription(label) {
-    this.manipulationDiv.appendChild(
-      this._createButton("description", "vis-button vis-none", label)
-    );
+    this.manipulationDOM["descriptionLabel"] = document.createElement("div");
+    this.manipulationDOM["descriptionLabel"].className = "vis-none";
+    this.manipulationDOM["descriptionLabel"].innerHTML = label;
+    this.manipulationDiv.appendChild(this.manipulationDOM["descriptionLabel"]);
   }
 
   // -------------------------- End of DOM functions for buttons ------------------------------//
@@ -948,10 +951,24 @@ class ManipulationSystem {
    * @param {Element} domElement
    * @param {Function} boundFunction
    */
-  _bindHammerToDiv(domElement, boundFunction) {
+  _bindElementEvents(domElement, boundFunction) {
+    // Bind touch events.
     const hammer = new Hammer(domElement, {});
     onTouch(hammer, boundFunction);
-    this.manipulationHammers.push(hammer);
+    this._domEventListenerCleanupQueue.push(() => {
+      hammer.destroy();
+    });
+
+    // Bind keyboard events.
+    const keyupListener = ({ keyCode, key }) => {
+      if (key === "Enter" || key === " " || keyCode === 13 || keyCode === 32) {
+        boundFunction();
+      }
+    };
+    domElement.addEventListener("keyup", keyupListener, false);
+    this._domEventListenerCleanupQueue.push(() => {
+      domElement.removeEventListener("keyup", keyupListener, false);
+    });
   }
 
   /**
diff --git a/test/network/maximumWidthEdgeCase.html b/test/network/maximumWidthEdgeCase.html
index df6aa4c57c..85a33688e8 100644
--- a/test/network/maximumWidthEdgeCase.html
+++ b/test/network/maximumWidthEdgeCase.html
@@ -1,5 +1,5 @@
 <!DOCTYPE html>
-<html>
+<html lang="en">
   <head>
     <title>Maximum Width Edge Case Test</title>
 
diff --git a/test/network/textMeasurementOnHoverTest.html b/test/network/textMeasurementOnHoverTest.html
index 04b55c0c7d..fcc525f995 100644
--- a/test/network/textMeasurementOnHoverTest.html
+++ b/test/network/textMeasurementOnHoverTest.html
@@ -1,5 +1,5 @@
 <!DOCTYPE html>
-<html>
+<html lang="en">
   <head>
     <title>Text Measurement Test</title>
 
diff --git a/test/networkTest.html b/test/networkTest.html
index 4938cb0f68..8f95b5d105 100644
--- a/test/networkTest.html
+++ b/test/networkTest.html
@@ -1,5 +1,5 @@
 <!DOCTYPE html>
-<html>
+<html lang="en">
   <head>
     <meta charset="utf-8" />
     <title>JS Bin</title>
diff --git a/test/network_unittests.html b/test/network_unittests.html
index fd20f7087b..3eb1e48cd4 100644
--- a/test/network_unittests.html
+++ b/test/network_unittests.html
@@ -1,6 +1,6 @@
 <!DOCTYPE html>
-<html>
-  <head lang="en">
+<html lang="en">
+  <head>
     <meta charset="UTF-8" />
     <title></title>
 
