#col_left {
	position:relative;
	float:left;
	width:150px;
	height:300px;
	border:1px solid blue;
	margin:2px 5px 2px 5px;
}
#col_right {
	position:relative;
	float:right;
	width:150px;
	height:300px;
	border:1px solid blue;
	margin:2px 5px 2px 5px;
}
#col_centre {
	position:relative;
	float:left;
	width:100%;
	border:1px solid orange;
}
#ctr_block {
	position:relative;
	float:left;
}
/* content definition to override global */