function addTarget() {
      if(!document.getElementsByTagName) {
          return false;
      }
      var links = document.getElementsByTagName("a");
      for(var i = 0; i < links.length; i++) {
          var link = links[i];
          if (link.getAttribute("href") && link.getAttribute("rel")=="external") {
              link.target = "_blank";
          }
      }
  }
  if (window.attachEvent) {
      window.attachEvent("onload",addTarget);
  } else if(window.addEventListener) {
      window.addEventListener("load",addTarget,false);
  } else {
      document.addEventListener("load",addTarget,false);
  }