First of all: don't ignore the warning, even when other browsers don't find anything suspicious (yet). When you can wait, then just wait some days until the warning is no longer shown!
What you're seeing Microsoft nowadays calls SmartScreen ("Phishing Filter" in IE7; technical details). There's a "More information" link, that you can safely click. You can also get this information manually:
- Go to a website that you want to check.
- Click the Safety button, point to SmartScreen Filter, and then click Check This Website.
IE uses some Microsoft database of bad websites. More of such databases exist. Like, though not specialized in all malware, PhishTank does not yield results for
ccollomb.free.fr. Google's Safe Browsing (as used in Firefox as well) does not find issues either, but: "The last time Google visited this site was on 2009-09-20". And StopBadware.org does not have the site listed either.
Still: maybe Microsoft found some recent (new) threat, or maybe it found some threat at some other subdomain of
free.fr and hence blocks all of that domain?
Note that even official websites might be compromised with malware, even when the website owner does not know about that.
So: click that "More information" link, it will tell you a bit more.
(If anyone knows of some website at which one can see what Microsoft has recorded about some URL: please tell us!)