app.css

.container {
    width : 1280px;
    background-color:crimson;
    margin:120px 80px 80px 80px;
    height:640px;
}

.footer {
position :absolute;
width: 1280px;
height: 144px;
left: 80px;
top: 760px;
background: #000;
}

.header {
    /* header */
    
    
        position: absolute;
        width: 1440px;
        height: 120px;
        left: 0px;
        top: 0px;
    
        background: rgba(60, 60, 60, 0.68);
}

xl - greater than 1440
lg - 768 to 1440
md - 480 to 768
sm - upto 480