url redirects

How to redirect visitors to another directory based on the URL given?

e.g. visitor goes to http://www.mysite.com/variable it should be redirected to http://www.mysite.com/subdirectory/variable

Many thanks in advance

This thread has been closed and replaced with the following thread:

Subject: Octothorpes in URLs
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Like in wikipedia, you can do things like
www.wikishit...articlename#section
to automatically scroll the page to the section. What HTML codan is responsible for this?