window.addEvent('resize', function(){
	update_vertical_center();
});

window.addEvent('load', function(){
	update_vertical_center();
});

function update_vertical_center()
{
	var win_size = window.getSize().size.y;
	var ele_size = $('outer_wrap').getSize().size.y;
	$('vertical_center_offset').style.display = (win_size > ele_size)? 'block' : 'none';			
}