style.css

body { 
    padding-top: 70px;
    background: url('http://www.associationcausefreudienne-vlb.com/wp-content/uploads/2016/07/fond-gris-sombre.jpg');
    background-repeat: no-repeat;
    background-size: cover;
    margin-left: 1%;
    margin-right: 1%;
}

 .fond {
    background: url('https://media.giphy.com/media/TvssierxunVyo/giphy.gif');
    background-size: cover;
    background-repeat: no-repeat;
    opacity: 0.9;
}  

.ecriture {
    color: white;
}

.Tchat {
    margin-top: 5%;
    margin-left: 5%;
    margin-bottom: 5%;
}

.fond1 {
    background-image: url('http://www.gamershell.com/static/streaming/18302/18302_medium.jpg');
    background-repeat: no-repeat;
    background-size: cover;
    padding-top: 2%;
}

.list-group-item-success {
    font-style: italic;
    text-align: center;
    margin-left: 3%;   
    background-color: #00800099;
    color: white;
}

.codeTry {
    background: url('https://www.cssdebutant.com/include/images/code.png');
    background-repeat: no-repeat;
    background-position: 5% 7%;
}

.codeTry2 {
    background: url('https://www.cssdebutant.com/include/images/code.png');
    background-repeat: no-repeat;
    background-position: 96% 99%;
}

.list-group-item-dark {
    background-color:#000000b3;
    color: white;
}

strong.toto {
    color: green;
}