lmo4103 - 5:26 pm on Sep 30, 2006 (gmt 0)

From now on, if your existing website can be reached with the leading www and without the leading www, then you need to choose your preferred address and make sure that the non-preferred address does a 301 redirect to the preferred one.

If you are setting up a new website, you should discuss the www v. no-www issue and get it set up so that it always resolves to the preferred way you have chosen.