//sample link in html
//<a href="http://www.google.com" onclick="centeredPopup(this.href,'Ticket Shop','500','500','yes');return false">Buy tickets online</a>
	
	var popupWindow = null;
		function centeredPopup(url,winName,w,h,scroll){
		LeftPosition = (screen.width) ? (screen.width-w)/2 : 0;
		TopPosition = (screen.height) ? (screen.height-h)/2 : 0;
		settings =
		'height='+h+',width='+w+',top='+TopPosition+',left='+LeftPosition+',scrollbars='+scroll+',resizable'
		popupWindow = window.open(url,winName,settings)
		}