var anArray;
    window.onload = function() {
      anArray = document.getElementById("ah").getElementsByTagName("a");
      for(var j=0;j<anArray.length;j++) {
        anArray[j].onclick = clickEventHandler;
        anArray[j].flag = true;
      }
    }
    function clickEventHandler() {
      if(this.flag) {
  this.style.backgroundImage = 'url(images/menu2_hover.jpg)';
        this.flag = false;
  for(var j=0;j<anArray.length;j++) {
    if (anArray[j] != this) {
      anArray[j].style.backgroundImage = 'url(images/menu2_bg.jpg)';
   anArray[j].flag = true;
    }
  }
        return;
      } else {
        this.style.backgroundImage = 'url(images/menu2_bg.jpg)';
        this.flag = true;
   }
    }