var shopNo  = new Image(); shopNo.src  = '/images/shop.gif';
var shopYes = new Image(); shopYes.src = '/images/shop_on.gif';
var aboutNo  = new Image(); aboutNo.src  = '/images/about.gif';
var aboutYes = new Image(); aboutYes.src = '/images/about_on.gif';
var ebooksNo  = new Image(); ebooksNo.src  = '/images/ebooks.gif';
var ebooksYes = new Image(); ebooksYes.src = '/images/ebooks_on.gif';
var eventsNo  = new Image(); eventsNo.src  = '/images/events.gif';
var eventsYes = new Image(); eventsYes.src = '/images/events_on.gif';

function over(which) {
  document.images[which].src = "/images/"+which+"_on.gif";
}
function out(which) {
  document.images[which].src = "/images/"+which+".gif";
}