If you do web design, making your pages work in different browsers can be very frustrating. The most common troublemaker is Internet Explorer and I think everyone who's ever tried hand-coding CSS has experienced. Another thing that makes it hard is simply lack of time to test it in all different browsers and platforms.
But! if it makes you feel any better even Apple is struggling as this screenshot shows.
I've seen Apple.com/store work in Firefox on other computers so clearly it's not a problem on all Firefoxes but you'd think a big site like this must have heard of this and done something about it. If you think that what happens is that the images aren't loaded that not the case. This problem has been around for a while for me now. And no, I don't have Firebug or any other debuggers switched on as I open this site.