Ever wanted to put a URL in documentation that neither points to a 'real' website nor will accidently send your more curious readers to, say, seventy pop-up windows of pr0n? Try example.com:

You have reached this web page by typing 'example.com', 'example.net', or 'example.org' into your web browser.

These domain names are reserved for use in documentation and are not available for registration. See RFC 2606, Section 3.

Good to know.