var myChild;

function openWindow(thisURL) {
  var childName = 'win';
  var childFeatures = 'toolbar=0,location=0,directories=0,status=0,menubar=0,scrollbars=1,resizable=1,width="580,height=450';
  var noGoodBrowser = false;

  if((navigator.appName == "Netscape" && parseInt(navigator.appVersion) == 2) || (navigator.appName == "Microsoft Internet Explorer" && parseInt(navigator.appVersion) == 3)) {
    noGoodBrowser = true;
  }

  if(myChild && !myChild.closed) {
    // child is present and still open.
    // change location, regain focus.
    // child & parent must share same domain (security policy).
    myChild.location = thisURL;
    myChild.focus();
  } else if(!noGoodBrowser) {
    myChild = window.open(thisURL, childName, childFeatures);
  }
}