function prepareMenu(){
  if( document.getElementById && document.getElementsByTagName ){
    if( document.getElementById('nav') ){
      var navdiv = document.getElementById('nav');
      var navitems = navdiv.getElementsByTagName( 'a' );
      for( var i=0; i < navitems.length; i++ ){
        navitems[i].onmouseover = function(){
          menuon(this);
        };
        navitems[i].onmouseout = function(){
          menuoff(this);
        };
      }
    }
  }
}

window.onload = prepareMenu;

function menuon(item){
  var curSrc = item.childNodes[0].src;
  var newSrc = curSrc.replace("1.gif", "2.gif");
  item.childNodes[0].src=newSrc;
}


function menuoff(item){
if(item.className!="on"){
  var curSrc = item.childNodes[0].src;
  var newSrc = curSrc.replace("2.gif", "1.gif");
 item.childNodes[0].src=newSrc;
}
}