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;
	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;