In the page that you want to be popped up, paste the following code at the top of your page :
You can modify the size of the popup screen.

<SCRIPT LANGUAGE="JavaScript"><!-- Begin function popUp(URL) { day = new Date(); id = day.getTime(); eval("page" + id + " = window.open(URL, '" + id + "', 'toolbar=0,scrollbars=1,location=0,statusbar=0,menubar=0,resizable=0,width=400,height=400');"); } // End --> </script>

Now for the link to the pop up, use the following code (change the yourlink here and nameoflink to your link and link name):

<A HREF="javascript:popUp('yourlinkhere')">Nameoflink</a>