My shell account at Dreamhost was compromised and this site was vandalized. It appears this was a wide spread event and a number of other sites hosted at Dreamhost were affected. If you have an account at Dreamhost, I recommend you change your passwords for your shell and email and check your web content for modifications.
I’ve cleaned up the mess (I think). Although as far as I can tell the Spider.xpi was not modified, I have generated a new version of Spider 0.0.2.7 to force an update to any Spider users.