function appendClass(element,value) {
    if (!element.className) {
        element.className = value;
    } else {
        newClassName = element.className;
        newClassName+= " ";
        newClassName+= value;
        element.className = newClassName;
    }
}

function highlightLinks() {
   var anzHrefs = document.getElementsByTagName("a").length;
   for (var i = 0; i <= anzHrefs - 1; i++) {
      if (document.getElementsByTagName("a")[i].href == document.location.href) {
         appendClass(document.getElementsByTagName('a')[i],"aktiv");
      }
   }
}