/* ブラウザサイズ取得 http://jquery.com/demo/thickbox/ 参照　*/
function getPageSize(){ 
	var de = document.documentElement;
	var w = window.innerWidth || self.innerWidth || (de&&de.clientWidth) || document.body.clientWidth;
	var h = window.innerHeight || self.innerHeight || (de&&de.clientHeight) || document.body.clientHeight;
	objPageSize = {width: w, height: h};
	return objPageSize;
}

document.write('<div id="cover">　</div>');
document.getElementById('cover').style.height = getPageSize().height;