You've not said which browser you're using. Internet Explorer is notorious for having problems with displaying images. Sometimes simply restarting your Pc will fix the problem. Otherwise running System Restore might help. It's also worth checking whether Internet Explorer has mysteriously switched off the 'Show pictures' option. The following instructions are for IE5 but later versions are probably similar:
Go to Tools > Internet Options > Advanced.
Under 'Multimedia', check that there's a tick alongside 'Show pictures'. If there's not, click to insert one, then click 'Apply' and 'OK'. (If there's already a tick there, as there should be, try removing it and clicking 'Apply' and 'Ok'. Close IE and restart your PC. Then go through the process again, to put the tick back).
However, the reason that many people move away from Internet Explorer, to an alternative browser, is frequently related to problems with displaying images. (It's certainly why I switched browsers). The majority of the 'regulars', on this site, use Firefox (which, for me at least, has never exhibited any problems with the display of images):
http://www.mozilla-europe.org/en/firefox/
Chris