function make_external_targetblank() {
var myDomain = document.domain;
var a = document.getElementsByTagName("a");
var x = a[1].href.search(myDomain)
for(var i=0; i<a.length; i++) {
  if (a[i].href.length < 1) { continue; }
  var h = a[i].href.toLowerCase();
  if( h.search(myDomain) < 0 ) {
    a[i].target = '_blank';
  }
}
}

//add load event
function ms_addLoadEvent(func) {
    var oldonload = window.onload;
    if (typeof window.onload != 'function') {
        window.onload = func;
    } else {
        window.onload = function() {
            if (oldonload) {
                oldonload();
            }
            func();
        }
    }
}

ms_addLoadEvent(make_external_targetblank)