function openOverlay()
{
	document.getElementById('content').style.display = 'block';
	document.getElementById('content').style.height = 520;
	document.getElementById('content').style.width = 680;
	document.getElementById('content').style.top = (document.body.clientHeight-520)/2;
	document.getElementById('content').style.left = (document.body.clientWidth-680)/2;
	document.getElementById('background').style.display = 'block';
}

function closeOverlay()
{
	document.getElementById('content').style.display = 'none';
	document.getElementById('background').style.display = 'none';
}