Go here with your browser of choice.
Depending on your browser's interpretation of the backslash character, you
will be taken to one of two pages.
Note that servers shouldn't actually pass bare backslashes as part of the URI. The `legal' version of the link is back%5Cslash.
On a separate topic, follow this
link with your browser of
choice (please note that this contains a space and is actually an illegal
URL, even if your browser has rewritten it to be standards-compliant). Lynx is
notorious for not rewriting hrefs, and thus confusing the server.
Now compare/contrast the result with what happens when you follow this link, which contains a space escaped as '%20'.
What do you do when you see URLs in a plain-text medium, such as Usenet - in particular, when they appear within sentences? Consider the URL http://theanna.org/slash/dot. URLs of that type being particularly problematic... Try that URL out and see for yourself.
For other stuff on the site, please go here.