<a href="..." class="popup">xxx</a>

window.onload=prepareLinks;

function prepareLinks()
{
	var links = document.getElementsByTagName("a");
	for(var i=0; i<links.length; i++){
		if(links[i].getAttribute("class")=="popup"){
			links[i].onclick = popupMyWin;
		}
	}
}
	
function popupMyWin()
{
popup(this.getAttribute("href"));
return false;
}