Importance of 'www' in domain name
 

I've noticed something strange about the way Google handles PR and backlinks for my domains...

For example, when I go to http://www.adult-sex-sites.net I get PR5 and 1,610 back links.

But, when I go to http://adult-sex-sites.net, I get PR1 with only 1 backlink.

Does anyone have an explanation for this...and can it affect SERPS?

Thanks!

domain.com and www.domain.com are treated as two different hosts with different index urls by Google, and thus have their own backlinks and PR... you need to try and aggregate all your incoming links (both internal and external) to one url - ie. usually http://www.domain.com/ with a trailing slash, so apache will serve the correct index page.

It will only affect your serps in that you are not competing with the full weight of all your pagerank if the PR is split between www and non-www versions.

Google doesn't seem to be doing that for one of my other domains...

http://www.free-sex-pix.net and
http://free-sex-pix.net both have the same PR and back links, as do

http://www.link-o-rama.com and
http://link-o-rama.com

It's mostly an issue of consistency of use. In the case you describe, most of the best links to your site are using the www.

But a few people are using linking without the www., and those linkers have lower pr, so google treats the two urls as different sites and assigns them different pr.

If no-one at all linked to you without the www, google sometimes seems to assume the www and non-www version are the same site, and gives them the same pr. (there could be other explanations for this effect...)

Not always, tho, one will often see one version with all the pr and the other with pr0.

Those domains that have equal pr on both versions usually have a broad base of incoming links using both www and non-www, giving both versions pr.

The usual approach to this is to try to make sure everyone links to you using the link you want to emphasize. Some choose the www, some the non-www.