Does the value come from the root of the domain or the URL it's actually on? Some forums have a PR of 6 but the profiles have 0.. Can anyone clarify?
It depends a lot. Google's algorithms are very complex and take many factors into consideration. For example a link from within an article that has PR0 but is on a PR7 domain will have a lot more value than a link from a PR0 (or even higher) profile page on a PR7 domain. Google does know where the link is - what type of page that is (profile, forum thread, blog post, etc.) and the location of the link (sidebar, footer, author name on comment, signature on forum, etc.). How do I know Google knows? Simple, I know as well. I can build a script to detect this with a very high accuracy. So to conclude, google does not take just one factor into consideration but the result a partial component of their system gives. For example during or after indexing a page, a component of Google's entire program might do something like this: Code: foreach link on page: if link is internal: if link is in text: link_value = 5; if link is in sidebar: link_value = 3; if link is external: if link is in content body: link_value = 5; if link is in sidebar: link_value = 3; if link is in comments: if comment spam detected: link_value = 0; else: link_value = 1; if link is in signature: if forum spam ammount > threshold: link_value = 0; else: link_value = 1; And I'm not even going into link relevance, page text relevance, site relevance, domain trust, and the other tens or hundreds of factors. Bottom line is, a context link from a PR0 page on a PR4 domain can be more valuable than a link from a PR1 profile of a PR7 domain. And that's not just because of the complexity of the algorythm but also because of latent factors like the fact that the page with the in-context link is more likely to receive backlinks from both that site and other sites, whereas the nobody has a reason to link to a profile page. However, profile links are useful. But for them to have a measurable effect on the SERPs, you need a lot of them. As always, the key is to get your hands on every **************** link you can. Get both high quality relevant links from powerful sites and high PR pages, but also a bunch of lower quality links (if you're in a situation where you have a hard time getting better links or you can automate/outsource the process). I hope this gives you an answer, even though it is not a simple answer.
Some of the value of the domain pr does flow through from pages that do not have any pr of their own which is why profiles links can be effective. As with any type of link though you should have a certain amount of variety. A very good article on links and how Google looks at them can be found at the url below. Interesting read. Code: http://www.seomoz.org/blog/10-illustrations-on-search-engines-valuation-of-links
O.P that is a loaded question, PR is not not everything. Link diversity is what has the most impact. Get links from pages with PR , and get links from pages that are no follow as well. Use different anchors texts as well, don't use the same one over and over mix it up. Get them from all sources and as many as you can. Of course don't over do a new site. Aged sites you can throw pretty much anything you want to at them.
