Website address with or without www?

Should we automatically convert www.example.com/abc.htm to example.com/abc.htm or vice-versa on the server side? Because user may type the site address with without www. Which is better?

EDIT: I'm asking because I'm writing many rewrite rules, so sticking to one is good I guess.

From serverfault $pageUsers[$entry.posts[0].author].name

• Whichever you like. In the old days, www.foo.com was preferred in order to distinguish web servers from ftp and other servers. Nowadays nobody really cares about that anymore. It's still good to accept both with and without the www prefix, though.

  From $pageUsers[$post.author].name

• there is absolutely no technical reason for adding www to your website. Its your choice to go with or without www because many popular websites with www like google, facebook. These websites redirect

  http://google.com to http://www.google.com
  

  Also there are many websites without www like twitter, stackoverflow.com. These redirect

  http://www.stackoverflow.com to http://stackoverflow.com
  

  I think you can choose to add or omit www

  One important point to note that

  You should have a permanent redirect rule to redirect from

  http://www.twitter.com to http://twitter.com
  

  This is because if you have show the content for both www.twitter.com and twitter.com

  Your search engine ranking would be split into two halves instead of twitter.com having 1000 ranks http://www.twitter.com would have 500 Ranks and http://twitter.com would have 500 ranks this spoils the popularity of the website.

  Btw Search engines would understand the redirect rule.

  Matt : +1 for the ranking - excellent point.

  danlefree : The ranking issue was a valid point (for MSN particularly) as recently as three years ago, however, you won't see this issue with major search engines any longer.

  nepsdotin : @abjeet why not consider accepting the answer ?
  From nepsdotin