Help my website got hacked!

[محروم.كوم]

Quote:
Not Found

The requested URL / was not found on this server.
Additionally, a 404 Not Found error was encountered while trying to use an ErrorDocument to handle the request.
Apache/2.2.11 (Unix) mod_ssl/2.2.11 OpenSSL/0.9.8e-fips-rhel5 mod_auth_passthrough/2.1 mod_bwlimited/1.4 FrontPage/5.0.2.2635 PHP/5.2.9 Server at neodestiny.net Port 80
Please tell me what I should do. I went to ask around and discovered that many sites of the same genre of mine have been hacked too like one of this:

Quote:
Forbidden

You don't have permission to access / on this server.

Additionally, a 403 Forbidden error was encountered while trying to use an ErrorDocument to handle the request.
Apache/2 Server at theneoplace.net Port 80
I don't think this is a ddos attack. How did the hacker hack into my site? My pw is at least 20 character long with all the up-to-date vb features.

Can someone help me on this?
Thanks __DEFINE_LIKE_SHARE__