function showOverlay(elementID) {
	document.getElementById(elementID).style.display='block';
	if (document.body.scrollHeight >= self.screen.availHeight)
	{
		document.getElementById(elementID).style.height = document.body.scrollHeight + "px";
		document.getElementById(elementID).style.width = document.body.scrollWidth + "px";
	}
	else
	{
		document.getElementById(elementID).style.height = self.screen.availHeight + "px";
		document.getElementById(elementID).style.width = document.body.scrollWidth + "px";
	}
}