Had a similar thing occur with a guestbook. Someone posted a "comment" that redirected into a hard core site, so no one could view the guestbook, or sign it, without been sent to this awful site.
Trouble was, somehow, they had also stopped their post appearing on the guestbook control panel so I couldn't delete the post or block the IP, in the end, the only option was to delete the guestbook and start afresh with a new guestbook, hopefully, with a better control panel!
Do have a go, just click where it asks and see how easy to 'spoof' a page in a frame on a trusted site ... Still happens after the latest M$ update (yesterday) .. KB834707.
Have FireFox 1.0 Preview Release with intent to trial next week.
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This appears to be a decent site which reports on security aspects. http://secunia.com/product/3256/#advisories
Select List of Patched/Unpatched Secunia Advisories Apparently
Two outstanding for FireFox 0.x
Have been using Firefox for approx 6 months now and use it as my main browser, some sites have problems with it, but not many. For the problem sites I now use Netscape Nav, I just wish you could remove IE from XP completely.
For E-mail, why not try Incredimail its free to download.
Microsoft have got a lot to answer for, but they have us by the b@lls as other systems are either too expensive or don't have the applications required.