.main_content {
	padding:10px;
	float:left;
	border-right:1px solid #E3E3E3;
	width:645px;
}
.extra_content{
	border-left:1px solid #E3E3E3;
	padding:10px 8px;
	float:left;
	clear:right;
	margin:0 0 0 -1px;
	width:300px;
}
	.extra_content #ad300x250box{
		width:300px;
		height:250px;
		overflow:hidden;
		background:#97989c;
	}