Fo3nix has correctly described the situation when things are working as they should. (i.e. the square with the red cross should only appear when there's an error on the website). However, where Microsoft programs are concerned, things rarely work as they should.
The problem of images not displaying in Internet Explorer is a common one. I encountered it, across several different PCs, with Windows 95, Windows 98 and Windows ME, using IE4, IE5 and IE6. I could occasionally manage to fix the problem by downloading the latest software updates from Microsoft but, eventually, the same problem would return.
These problems with image display were the reason I switched to using Firefox, rather than Internet Explorer. It's a much better browser and I've never experienced any problems with images not displaying:
http://www.mozilla.com/en-US/
If you really want to continue using Internet Explorer, I suggest downloading IE7.
Chris