sorry for the vague subject, but I couldn't find a better one.
I have the website http://digifreedom.net running on a Centos 4 VPS with Apache and Drupal 6.10 . This is a multisite Drupal setup: only one installation, with subdirectories in sites/, and a separate mysql database for each website. For several reasons, I had setup DNS, drupal and everything to work without the www prefix on domain names. In other words, http://digifreedom.net is OK, www.digifreedom.net was never used.
Everything worked perfectly for months, if not years. Five minutes ago, somebody wrote to me that a digifreedom.net URL I suggested him to read "doesn't work".
I checked, and what happens now is that, if I type http://digifreedom.net/node/82 the browser is immediately redirected to www.digifreedom.net/node/82, which (of course) returns an error message:
"Firefox can't find the server at www.digifreedom.net"
That error message is OK, because I had NOT set up DNS and apache to answer to that address. What I don't get is why http://digifreedom.net now becomes www.digifreedom.net. I haven't changed anything myself in DNS, drupal or apache config for many weeks, so why all of a sudden something started to behave differently?
The weirdest thing is that this "forced redirection" from example.com to www.example.com happens with some, but not all of the other domains configured in the same way and running on the same server off the same Apache/Drupal installation!
How can I find, at least, which piece of the puzzle is responsible for this problem? I am aware that probably this isn't even a centos issue, I just need a pointer in the right direction.
TIA, Marco