.clear{clear:both;}
#wrapper{width:800px;height:800px;background:#eee;}
#header{width:100%;height:80px;background:violet;}
#inner_wrapper{width:100%;}
#content{float:left;width:80%;height:640px;background:yellow;}
#sidebar{float:left;width:20%;height:640px;background:cyan;}
#footer{width:100%;height:80px;background:violet;}