function addLoadEvent(func) {
  var oldonload = window.onload;
  if (typeof window.onload != 'function') {
    window.onload = func;
  } else {
    window.onload = function() {
      oldonload();
      func();
    }
  }
}

function popUp(url) {
   newWin = window.open(url,'_blank','width=420,height=480,menubar=no,scrollbars=no,status=yes,resizable=yes');
   newWin.focus();
}

function externalLinks() {
   if (!document.getElementsByTagName) return;
   var anchors = document.getElementsByTagName("a");
   for (var i=0; i<anchors.length; i++) {
      var anchor = anchors[i];
      if (anchor.getAttribute("href") && anchor.getAttribute("rel") == "external")
         anchor.target = "_blank";
   }
}

// define onload events
addLoadEvent(externalLinks);