Robots.txt or other tools with outside sites

[508]

I have placed my website on different message boards. How can I use robots.txt or any other tool so the message boards cannot get indexed by a search engine?

[pcthug]

You cannot control whether or not an outside site is indexed by a search engine, the most you can do is add rel="nofollow" to any hyperlinks that you wish search engines to ignore

[TiGGi]

If you want to deny access to a directory add this to your robots.txt
User-agent: *
Disallow: /directory/

You can add as many directories as you want.
If you want to block crawlers from the whole site do this:

User-agent: *
Disallow: /