function close_overlay()
{
	var overlay_a = document.getElementById('overlay_a');
	var overlay_center_error = document.getElementById('overlay_center_error');
	var overlay_gray = document.getElementById('overlay_gray');
	var overlay_iframe = document.getElementById('overlay_iframe');
	
	if (overlay_a)
	overlay_a.style.visibility = 'hidden';
	
	if (overlay_center_error)
		overlay_center_error.style.visibility = 'hidden';
	
	if (overlay_gray)
	overlay_gray.style.visibility = 'hidden';
	
	if (overlay_iframe)
		overlay_iframe.style.visibility = 'hidden';
}