PageRank
PageRank is SERPS way of deciding a page’s importance or relevance, considered one of the most important element for Website Ranking. It is one of the factors that determines a page’s ranking in the search results.
PageRank is scored on a scale from 0-10. A PageRank of 0-3, usually pertains to small to mid-size companies and a PageRank of 4-6 refers to large international companies. PageRanks of 7 or above are reserved only for internet giants: Google, Facebook, Wikipedia, etc.
Here are some sites that can give some insite on your are websites ranking and where you need to make changes. 
- Alexa
- Compete
- CheckPageRank
- prchecker
More detailed information
- statmyweb (if you are looking for great information for FREE this Site can do alot for You it has everything alot ot the best enterprises website have to offer Great tool.)
- website market grader (this is based heavely off social interaction google has said social interaction plays little part on pageranking)
Google ranks websites by those that are deemed to have the most authority on the given topic/keyword.
Quote taken directly from Matt cutts off Googles site
The goal of many of our ranking changes is to help searchers find sites that provide a great user experience and fulfill their information needs. We also want the “good guys” making great sites for users, not just algorithms, to see their effort rewarded. To that end we’ve launched Panda changes that successfully returned higher-quality sites in search results. And earlier this year we launched a page layout algorithm that reduces rankings for sites that don’t make much content available “above the fold.”
Search Engines
Simply put SERPS looks at who's viewing you website and who is linking to a website and who you are linking to. Then they determine how highly it ranks. If important sites are linking to your website, you will rank much higher giving you more authority.Knowledge
You must know EXACTLY why the top 10 ranked sites in Google are currently ranked where they are. You can't guess by simply looking at their web page why they rank well you need to know.
Science
SEO is a science and pageranking it a big part of that without it you wont get the traffic you need or want in order to produce business.
When you think about SEO you need to be thinking about a long term plan for how you’re going to achieve ranking for search terms. It’s not instant pay off, but a long term commitment to produce good content.
Frequent blogging + content development = Quality Backlinks = Authority = High PageRank
GOAL: More Business More Traffic More Money!
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