Array.prototype.remove = function (elm) {
    for(var i=0; i < this.length; i++) {
      if (this[i] == elm) {
        this.splice(i,1);
        return;
      }
    }
  };
  function classAdd(obj,cName) {
    cs = getClasses(obj);
    cs.push(cName);
    setClasses(obj, cs);
  }
  function classRemove(obj,cName) {
    cs = getClasses(obj);
    cs.remove(cName);
    setClasses(obj, cs);
  }
  function getClasses(obj) {
    return obj.className.split(/\s+/);
  }
  function setClasses(obj, ary) {
    obj.className = ary.join(' ');
  }
  function rollon(obj,hoverClass) {
    classRemove(obj,'normal');
    classAdd(obj,hoverClass);
  }
  function rollout(obj,hoverClass) {
    classRemove(obj,hoverClass);
    classAdd(obj,'normal');
  }