#box{width:600px;border:2px solid pink;}
header{width:100%;height:100px;background:grey;}
#content{width:100%;height:400px;}
footer{width:100%;height:100px;background:yellow;}
#clear{clear:both;}

/** layout 1**/
#layout #left{width:50%;height:400px;background:green;float:left;}
#layout #right{width:50%;height:400px;background:orange;float:left;}

/** layout 2**/


/** layout 3**/