function reposition_on_scroll_div_cover() {
	var window_height = getWindowInnerHeight() ;
	var window_width = getWindowInnerWidth() ;
	var ScrollX = getScrollX() ;
	var ScrollY = getScrollY() ;	
	
	$('div_cover').style.width = window_width + ScrollX + "px" ;
	$('div_cover').style.height = window_height + ScrollY + "px" ;
}