I used a plug-in for jQuery that is preloading CSS images but actually it’s not working properly for IE and rollover of form buttons.

That’s why I found a better way to preload images and it’s 100% working for all browser. Here is the example:

jQuery.preloadImages = function() {  
     for(var i = 0; i<arguments.length; i++)  
    {
          jQuery("<img>").attr("src", arguments[i]);  
    }
}

To use the function you just have to use this:

$.preloadImages("image.gif", "/folder/image/another_image.jpg");