window.onload = function() {
// check to see that the browser supports the getElementsByTagName method
// if not, exit the loop 
if (!document.getElementsByTagName) {
return false; 
} 
// create an array of objects of each link in the document 
var popuplinks = document.getElementsByTagName("a");
// loop through each of these links (anchor tags) 
for (var i=0; i < popuplinks.length; i++) { 
// if the link has a class of "popup"... 
if (popuplinks[i].getAttribute("class") == "popup") { 
// add an onclick event on the fly to pass the href attribute 
// of the link to our second function, openPopUp 
popuplinks[i].onclick = function() { 
openPopUp(this.getAttribute("href")); 
return false; 
} 
}
} 
} 
function openPopUp(linkURL) {
window.open(linkURL,'popup','width=400,height=200')
}