NCRollOver = Class.create();
NCRollOver.prototype = {
  initialize: function() {
    // Observe clicks on our list items     
    $$('a.menu').each(function(item) {
      Event.observe(item, 'mouseover', this.rollOver.bindAsEventListener(this));
	  Event.observe(item, 'mouseout', this.rollOut.bindAsEventListener(this));
    }.bind(this));
  },

  // Arbitrary functions to respond to events
  rollOver: function(event) {
    var img = Event.element(event).readAttribute('src')
	img = img.replace(/_o.gif/, ".gif");
	img = img.replace(/.gif/, "_o.gif");
    Event.element(event).writeAttribute('src', img).show();
  },

  rollOut: function(event) {
    var img = Event.element(event).readAttribute('src')
	img = img.replace(/_o.gif/, ".gif");
    Event.element(event).writeAttribute('src', img).show();
  }
}