Dirk was the first to tell me that there was something wrong with the layout of this site in Internet Explorer : some links could not be clicked, like the one in the 'Top 2005 space images' post. I immediately thought of a typo in the specification of the link, but a quick check told me that this was 100% valid HTML code. So the error must be in the stylesheet. I replaced it with the default one in Drupal, and made some minor cosmetic changes. Seems to work better now in Internet Explorer, though the issue isn't completely solved.