function popup(w,h,site) {
			x=screen.availWidth/2-w/2;
			y=screen.availHeight/2-h/2;
			var popupWindow=window.open('','','width='+w+',height='+h+',left='+x+',top='+y+',screenX='+x+',screenY='+y);
			popupWindow.document.write(site);	
		}