// Add .first to the first item element for all list elements.
var Lists = {
  classifyFirstItems: function() {
    $$("ul, ol").each(function(element) {
      var li = element.down("li");
      if (li) {
        li.addClassName("first");
      }
    });
  }
}

document.observe("dom:loaded", function() {
  Lists.classifyFirstItems();
});