function getDocHeight() {
    var D = document;
    return Math.max(
        Math.max(D.body.scrollHeight, D.documentElement.scrollHeight),
        Math.max(D.body.offsetHeight, D.documentElement.offsetHeight),
        Math.max(D.body.clientHeight, D.documentElement.clientHeight)
    );
}

	
	function resizeBody(){
		var v=getDocHeight();
		document.getElementById("page_bg").style.height=(v-280)+'px';
	}