JS.
<style>
body, html, div{
margin: 0;
padding: 0;
}
.stretch{
position: absolute;
bottom: 0;
top: 0;
left: 0;
right: 0;
}
#container{
background: #DDD;
overflow: hidden;
}
#menu{
background: #FF0000;
width: 100%;
height: 50px;
}
#content{
top: 50px;
width: 100%;
background: #AAA;
}
#left{
background: #00FF00;
width: 20%;
overflow: auto;
}
#left-content{
background: rgba(0,0,0,0.4);
height: 500px;
}
#right{
background: #0000FF;
width: 80%;
left: 20%;
overflow: auto;
}
#right-content{
background: rgba(0,0,0,0.4);
height: 1000px;
width: 3000px;
}
</style>
<div id="container" class="stretch">
<div id="menu">Menu</div>
<div id="content" class="stretch">
<div id="left" class="stretch">
<div id="left-content">Left</div>
</div>
<div id="right" class="stretch">
<div id="right-content">Right</div>
</div>
</div>
</div>
: JS Bin:)