.clear{clear:both;}
#wrapper{width:800px;height:600px;background:pink;}
#header{width:100%;height:100px;background:cyan;}

#content{width:800px;height:400px;background:blue;}
#left_side_bar{width:100px;height:400px;background:gray;float:left;}
#right_side_bar{width:100px;height:400px;background:yellow;float:left;}

#first{width:100px;height:400px;background:brown;float:left;}
#second{width:100px;height:400px;background:silver;float:left;}
#third{width:50px;height:400px;background:black;float:left;}

#footer{width:100%;height:100px;background:orange;}