function PopupWindow(URL, title, sizeX, sizeY) 
{
	// Center window
	var posX = (screen.availWidth - sizeX) / 2;
	var posY = (screen.availHeight - sizeY) / 2;
	window.open(URL, title, "left=" + posX + ",top=" + posY + ",width=" + sizeX + ",height=" + sizeY + ",dependent=yes,resizable=yes");
}
		
function ShowImpressum()
{
	PopupWindow("./impressum.html", "Impressum", 400, 300);
}