<div id="layout">
   <div class="left-layout">I am at left side with 50% width</div>
   <div class="right-layout">I am at right side with 50% width</div>
</div>

div#layout{
   width: 100%;
   height: 100%;
   background-color: yellow;
}

div#layout div {
   float: left;
}

div#layout .left-layout {
   background-color: wheat;
   width: 50%;
   height: 100%;
}
div#layout .right-layout {
   background-color: green;
   width: 50%;
   height: 100%;
}

body {
   margin: 0px;
   padding: 0px;
   outline: none;
}