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() {
	  if (document.all)
        var xMax = screen.width, yMax = screen.height;
		else
        if (document.layers)
            var xMax = window.outerWidth, yMax = window.outerHeight;
        else
            var xMax = 640, yMax=480;

		var xOffset = (xMax)/2, yOffset = (yMax)/2;
		// Next two lines should be on one line
        self.open(this.href, "",
          'width=591,height=487,screenX='+xOffset+',screenY='+yOffset+',top='+yOffset+',left='+xOffset+'');
        return false;
      }
    }
  }
}
window.onload=doPopups;