// <a href="html-or.jpg" onclick="return popup(this,123,456)" title="..." // or 
// <a href="html-or.jpg" onclick="return popup(this)" title="..." 

var pop = null; 
function popdown() 
{
 if (pop && !pop.closed) pop.close(); 
} 

function popup(obj,w,h) 
{ 
 var url = (obj.getAttribute) ? obj.getAttribute('href') : obj.href; if (!url) return true; 

 w = (w) ? w += 20 : 150; // 150px*150px is the default size 
 h = (h) ? h += 25 : 150; 
 var args = 'width='+w+',height='+h+',resizable'; 
 popdown(); 
 pop = window.open(url,'',args); return (pop) ? false : true; 
} 
window.onunload = popdown; 
window.onfocus = popdown;