$(window).resize(function(){
  resizeBG();
});
$(window).load(function(){
	resizeBG();
});
function resizeBG() {
	$('#gray_bg').height($(document).height());
	$('#gray_bg img').height($(document).height());
	//$('#gray_bg').height($('#cnt').height());
	//$('#gray_bg').height($(document).height());
}