addLoadEvent(toggle_menu_load);

function toggle_menu_load() {
  var trigger_images = document.images;
      for ( i=0;i < trigger_images.length;i++) {
        if (trigger_images[i].className.indexOf("menu_trigger_icon") > -1) {
          trigger_images[i].onclick = toggle_menu;
        }
      }
}

function toggle_menu() {
  var toggle_div = document.getElementById(this.id+"_2");
   if (toggle_div.style.display == "block") {
       toggle_div.style.display = "none";
       swapImage(this);
   }
   else {
        toggle_div.style.display = "block";
       swapImageBack(this);
   }


}

function  swapImage(toggle_image) {
  toggle_image.src="http://crewandhowell.com/images/plus.bmp";
}

function  swapImageBack(toggle_image) {
  toggle_image.src="http://crewandhowell.com/images/minus.bmp";
}