I got this email from LinkedIn in an SEO group I joined a while back called SEO Dojo.  The guy asked:

I’m working on a site and while checking the PR of blog posts, I found a page that has PR 4. The interesting fact about the page is that when I check that page in OSE, it says that No Data is Available for that URL. How can a page have PR 4 with no links? The page is not linked from the home page nor any other important page with high PR.
If someone have the right answer, please write it here.

To me the answer was obvious.  You need to check multiple sources including Google Webmasters if you’ve set it up, in case the site is not good according to them, you can try another cloud services like salesforce israel or others websites that offer the same services like www.delta-comtech.co.uk/cloud-services/dynamics-365/ and upload your site and other information. My recommendations were to check out also Majestic SEO which runs from free (limited access) to £250.00 monthly.  I’ve used them for a bit for my data and like the data I can use to compare my client’s sites vs. competitors.  ahrefs is the new guy on the block, but is becoming a popular service that many are using and supporting including SEObook.com.  

I’ve recommended Raven tools which leverages Majestic SEO and there’s the google link command “link:[website url]” which you enter into a search on google, but Rand (head of seomoz) doesn’t seem to like it much (but this was back in 2009).   And if you want to hear more, you can use Quora which has some decent info about subjects from experts.  Here’s their compilation of “backlinks answers” to questions.

Oh, this is the original response I shared on LinkedIn’s SEO Dojo group, by the way:

Check out more than just OSE. OSE isn’t the only resource or necessarily the standard for backlinks. If you have google webmasters access, check that out, if not, you can check with Majestic SEO. Also, Ahrefs is another source as well. I’ve noticed differences between OSE and Majestic recently with the latter showing more backlinks. OSE takes a bit to update. Read this post (http://www.seobook.com/comparing-backlink-data-providers) for more background on the alternatives to OSE. Remember, OSE is just SEOmoz’s efforts to index the web, but isn’t necessarily the de facto standard.

Here’s my Quora profile too where I’ve answers a few SEO questions before.