function apri(link,w,h) {

	if (isNaN(arguments[1])) 
		w=800;

	if (isNaN(arguments[2]))
		h=600;

        mywin = window.open(link,'','scrollbars=yes,resizable=no,screenX=40,left=40,screenY=20,top=20,InnerWidht='+w+',width='+w+',InnerHeight='+h+',height='+h+',status=no,location=no,toolbar=no,menubar=no');

}

<!-- Paste this code into an external JavaScript file named: popUp.js  -->

/* This script and many more are available free online at
The JavaScript Source :: http://javascript.internet.com
Created by: Travis Beckham :: http://www.squidfingers.com | http://www.podlob.com */

/* Created by Jeremy Keith
  http://domscripting.com */
function doPopups() {
  if (!document.getElementsByTagName) return false;
  var links=document.getElementsByTagName("a");
  for (var i=0; i < links.length; i++) {
    if (links[i].className.match("popup")) {
      links[i].onclick=function() {
			window.open(this.href, "", "scrollbars=yes,top=0,left=0,width=1000,height=700,InnerWidth=1000,InnerHeight=700,toolbar=no,menubar=no,location=no,status=no");
        return false;
      }
    }
  }
}
window.onload=doPopups;