SuzyUK - 6:08 am on Nov 6, 2006 (gmt 0)

I read that it is optional for a UA to download images with, or inside any element with, the setting of display: none; - Opera seemingly have taken the option not to.

You can achieve preloading via other CSS methods if you still need to, e.g absolutely position that hidden div "off left" :

.hidden {
position: absolute;
left: -9999px;
}

or depending on your Gallery application you might be able to position the images where they're supposed to be and use z-index to toggle their display? (you can only use z-index on a relatively or absolutely positioned element)