*{padding:0; margin:0;}
.block{
	height:100px; 
	border:3px solid black;
	}
#wrapper{
	width:500px;
	position:relative;
	margin-right:auto;
	margin-left:auto;
}
#yellow{
	background-color:yellow;
	position:relative;
	right:100px;
	}
#red{
	background-color:red;
	width:100px;
	height:500px;
	}
#green{
	background-color:green;
	position:absolute;
	left:400px;
	top:0px;
	height:500px;
	width:100px;
	}
#blue{
	background-color:blue;
	position:absolute;
	width:500px;
	top:505px;
	left:105px;
	}