function swap(e)
{
  var image = Event.element(e);
  try { image.src = (image.src.include("off"))? image.src.gsub("off","on"): image.src.gsub("on","off"); }
    catch ( err ) { }
}
function init()
{
  Event.observe( $('simplicity'), 'mouseover', swap);
  Event.observe( $('simplicity'), 'mouseout', swap);
  Event.observe( $('balance'), 'mouseover', swap);
  Event.observe( $('balance'), 'mouseout', swap); 
  Event.observe( $('power'), 'mouseover', swap);
  Event.observe( $('power'), 'mouseout', swap);  
}

Event.observe(window, 'load', init);