function displayPopin(address, params) {
	var popin = document.getElementById('popin');
	if (!popin) {
		popin = document.createElement('div');
		popin.id = 'popin';
		popin.style.display = 'none';
		popin.style.position = 'absolute';
		popin.style.zIndex = 9;
		document.body.insertBefore(popin, document.body.firstChild);
	}

	if (window.XMLHttpRequest) {
		var request = new XMLHttpRequest();
		request.open( "GET", address + '?' + params, true );
		var body = params;
		request.send( body );
		request.onreadystatechange = function() {
			popin.innerHTML = request.responseText;
			showOverlay(hidePopin);
			popin.style.display = '';
			centerLayerInViewport(popin.id);
		}
	} else  {
		new Ajax.Request(
			address,
			{
				method: 'get',
				parameters: params,
				evalJSON:false,
				sanitizeJSON: false,
				evalJS: false,
				onSuccess: function(originalRequest) {
					popin.innerHTML = originalRequest.responseText;
					showOverlay(hidePopin);
					popin.style.display = '';
					centerLayerInViewport(popin.id);
				}
			}
		);
	}
}

function hidePopin() {
	if ($('popin')) { $('popin').style.display = 'none'; }
	if ($('overlay')) { $('overlay').style.display = 'none'; }
}

function showOverlay(onclick) {
	var overlay = document.getElementById('overlay');
	if (!overlay) {
		overlay = document.createElement('div');
		overlay.setAttribute('id','overlay');
		overlay.style.display = 'none';
		overlay.style.position = 'absolute';
		overlay.style.top = '0px';
		overlay.style.left = '0px';
		overlay.style.zIndex = '8';
	 	overlay.style.width = '100%';
	 	if (document.all) {
	 		overlay.style.backgroundColor = 'transparent';
		 	overlay.style.filter = 'progid:DXImageTransform.Microsoft.AlphaImageLoader(src="/themes/default/images/overlay.png", sizingMethod="scale")';
	 	} else {
	 		overlay.style.backgroundImage = 'url("/themes/default/images/overlay.png")';
	 	}
		document.body.insertBefore(overlay, document.body.firstChild);
	}
	if (!onclick) {
		overlay.onclick = hideOverlay;
	} else {
		overlay.onclick = onclick;
	}
	overlay.style.height = (getPageHeight() + 'px');
	overlay.style.display = 'block';
}

function hideOverlay() {
	var overlay = document.getElementById('overlay');
	if (overlay) {
		overlay.style.display = 'none';
	}
}