I just noticed this page in my web server a few minutes ago, has my site been hacked? Looks similar to this: http://spiderman.co.nz/ http://www.all4sides.com/gh.html
Well, doh, but I sware, someone will have have hell to pay if I find out who the heck they are... and I know I won't, but honestly, any kid could have done that, uploading a page when the content was still writable. And I don't want to turn this into a religious argument but it definitely does not appear that this was simply a random attack by a bored little kid. :-?
writeable or not it's called site security... loopholes are there and injections can be made... Could also simply be a user/pass hack that worked!!
You need to thank God that he haven't defaced your entire index files, He just left a slight warning that you should secure your hosting. Because everyone is not that good to warn, If it was someone else would have defaced your entire site.