Www vs nonwww domain

[GreenBirdMedia]

Since about 5 years out site was launched as "www.example.com" but last June 2012, we relaunched new design but somehow went without www subdmain - "http://example.com".

We didn't check that time but now find duplicate pages and very confused what next.  Please answer:

1. Do search engines penalize for the change of domain name? www.example.com vs example.com?

2. How can go back (or, should we really?) to www.example.com?

3. I did redirect .htaccess rewrite from nonwww to www - but now our site is launched as without www.

4. Confused so Please advise ASAP.

Thanks a Million

[GreenBirdMedia]

my domain.com/sitemap shows all without www but I had .htaccess rewrite on and forwarded all nonwww to www just about 2 days back.

Ranking didn't seem to have affected much as of now - please help.

[josh-riley]

Going back may not solve anything, given that enough time may have passed that enough content has been indexed and the "damage is done" so to speak.

The 301 redirect is a good step - search engines don't penalize, the issue is just that you essentially confused things and you have to now untangle, like with the duplicate pages and content.

You #3 - I'm not sure I am following, so getting back to the redirect, if you were previously "www" and now are without, then the "www" pages should redirect to the without URLs. It sounds like there may be a risk of a redirect tangle going on that needs to be fixed?

Once the redirect situation is taken care of, pull together a site map for the "www" (if you can) and upload it to Webmaster so Google knows to index those pages and then can make the association that you changed domains.