function imgMenuEffect ()
{
  var allImg = document.getElementsByTagName("img");
  var menuImg = new Array();
  for (var i = 0; i < allImg.length; i++)
  {
    if (allImg[i].className == "img_menu")
    {
      allImg[i].onmouseover = function() {
        this.src = this.src.split(".gif")[0] + "_active.gif";
      };
      allImg[i].onmouseout = function() {
        this.src = this.src.split("_active.gif")[0] + ".gif";
      };
    }
  }
}

window.onload = imgMenuEffect;