On PageRank

Figuring out how PageRank works is much easier if you think of each web page individually. PageRank measures the relationship between pages, whether they’re part of your web site or part of someone else’s.

So, think in terms of web pages, not web sites.

The first thing you need to understand: Links are votes. A link from one page to another is a vote by the first page for the authority of the other. So, one lonely page, with no links in or out, has no votes. It’s very unlikely to make its way into a search engine index

PageRank is a finite resource. Every link on a page expends some of that page’s PageRank. That means you have less to give.

That’s why, even for onsite SEO, you have to understand PageRank. You need to carefully structure your sites to conserve PageRank, and send it where it’s most needed. Google+