html, body {
    padding: 0px;
    margin: 0px; 
}           
#container {
    width: 100%;
    height: auto;
    overflow:hidden;        
}
#header {
    background-color: green;
	width: 100%;
    height: 100px;
}
#content {
    background-color: blue;
    width: 100%;
}
#footer {
    background-color: purple;
    width: 100%;
    height: 50px;
    float:left;
}
#content div {
    float: left;
    width: 50%;
    height: 150px;
}            
.leftcol { 
    background-color: yellow;
}
.rightcol {
    background-color: orange;
}