I was just approving some website listings on MadisonClick and still continue to notice websites that have both the "www" and non-www version of their URLs working.
You really need to stick with one or the other and not have both working. Google does seem to now pick which domain is favored, but you still could get penalized for having duplicate websites out there. Matt Cutts explains this well:
Q: What is a canonical URL? Do you have to use such a weird word, anyway?
A: Sorry that it’s a strange word; that’s what we call it around Google. Canonicalization is the process of picking the best url when there are several choices, and it usually refers to home pages. For example, most people would consider these the same URLs:
But technically all of these URLs are different. A web server could return completely different content for all the URLs above. When Google “canonicalizes” a URL, we try to pick the URL that seems like the best representative from that set.
What you want set up, to keep things neat, clean and to cause no confusion with Google or other search engines, is a redirect in place which forwards one to the other. It's called a "301 Redirect" and it's the proper way to clean this up. It also automatically forwards people to the right domain (whichever one you choose) in case they add or forget to add the "www" when going to your website. We do this with every website we set up.
Another thing we seem to run into every so often is a company that has wisely purchased a bunch of domains that relate to their business. It's smart to do that but sometimes what they've done is set them up in such a way that each domain name points to the same content. It does not redirect to one, main website but instead shows the same content under each domain. This is another way where you could get penalized and lose search engine rankings but having sites out there with duplicate content - at least that's how search engines will see it.
With the way our website hosting is set up, you can't really do this unless the configuration is changed. So, by default it will work correctly. This isn't so with all website hosts out there.
If you think you may need some help with how your website is set up, please contact Webstix today. If you make the change now and do it right, then things can get restored and you can start to see improved rankings in the following months... yes, it can sometimes take that long - so there's no reason to wait any longer.
UPDATE: Oh, no. Another website design company in Madison just submitted their website to MadisonClick and the non-www version of the site, which they submitted, didn't work. The www version worked though, so I fixed that for them. I just thought that was strange since I just blogged about this. They have just one version, which is good but it brings up the point that you need to make sure both versions do work. So something else to make sure of and it gave me a chance to add that point here.