Suggestions

[aceres]

Seemed to work in Chrome (could be coincidental) but not Firefox.

Is this the codes?

Code:

$(window).load(function() {
         $('<img/>').src = '/resources/images/bg/content-shadow.png';
         $('<img/>').src = '/resources/images/bg/shadow.png';
         $('<img/>').src = '/images/bg/mushrooms.png';
         $('<img/>').src = '/resources/images/bg/header.png';
         $('<img/>').src = '/resources/images/bg/content.png';
         $('<img/>').src = '/images/bg/shadow.png';
         $('<img/>').src = '/resources/images/bg/footer.png';
         $('<img/>').src = '/resources/images/display/icon-background.png';
      });

I don't know jQuery but doesn't this try to preload into same object or something? Another things is perhaps "window.load" is causing problems for Firefox (might be waiting for window fully loaded)? Maybe try something like this without jQuery:

Code:

var preloadimages = new Array();
preloadimages[0] = new Image(); preloadimages[0].src = '/resources/images/display/icon-background.png';

If this works, copy the 2nd line and iterate the index for every image.