Firefox not preloading background images

Mozilla Firefox is a great internet browser, and I just love tabbed browsing. Each day I look in Bloglines to see which sites have been updated, and I open up all interesting reading matter in new tabs — I CRTL-click more than I click. After that I go one by one through my tabs, reading each page and opening interesting links in new tabs. I continue doing so until I have closed all my tabs, or until I run out of time, in which case I simply bookmark all open tabs. The good thing about loading pages on tabs it that I can load many pages before I read them; each time I close a tab, I find a new page waiting for me.

But there is one thing that annoys me. As you might know, I am very interested in web design, and many sites I read are about standards web design. Therefore, more and more sites I visit are standards compliant: clean HTML and designed with CSS. In my opinion Firefox does not handle these sites correctly, since it only starts loading background images the moment I focus on a tab. Thus many times I close a tab, I am confronted with an almost white page with some text on it, which then is converted little by little in a beautiful design. I do not understand why Firefox waits until I focus on the tab and does not pre-load the background images while I am reading other sites.

Or is there some hidden configuration option I don’t know about?

Jeroen Sangers @jeroensangers