index.css

div.main{
position:relative;
max-width: 1700px;
width: 100%;
height:1000px;
border:4px solid black;
}

div.sub1{
background-color:green;
position:absolute;
height: 100%;
display:inline-block;
margin-left:200px;
width:100%;
border: 1px solid black;
max-width:1500px;
}

div.side{
float:left;
background-color:blue;
position:absolute;
display:inline-block;
width: 200px;
border: 1px solid black;
height: 100%;
}