// Open popup window
function OpenWindow(PageName, width, height)
{ 		

	if (isNaN(width))
	{
		width	= Math.round(screen.width*4/5);
	}

	if (isNaN(height))
	{
		height 	= Math.round(screen.height*4/5);
	}
			
	var
	left 	= (screen.width - width)/2,
	top 	= (screen.height - height)/2;
				
	window.open(PageName, "darktower", "location=0, directories=0, menubar=0, toolbar=0, scrollbars=1, noresize, width="+width+", height="+height+", left="+left+", top="+top);

	return false;
}