Google Page Rank
Google defines it as:
PageRank reflects our view of the importance of web pages by considering more than 500 million variables and 2 billion terms. Pages that we believe are important pages receive a higher PageRank and are more likely to appear at the top of the search results.
PageRank also considers the importance of each page that casts a vote, as votes from some pages are considered to have greater value, thus giving the linked page greater value. We have always taken a pragmatic approach to help improve search quality and create useful products, and our technology uses the collective intelligence of the web to determine a page's importance.
In short, your site's Google PR is measured by it's relevance, imporance and mostly, relevant back links. The actual PR of a site is updated very frequently by Google. Although I can't say when or how frequent. Let me rephrase that, actually only a select few in Google knows when the updates happen. Google uses a very complicated algorithm to compute a site's Google PR. The method of measurement is based on a 0-10/10 ranking.
Pages with 0/10 Google PR have been considered by their search engine as useful or relevant sites depeding on the category of the site in question. It make take for atleast 3-12 weeks before a sites PR is considered by Google's search engines. Now, what's the difference of a 'unranked' page is basically a new page and Google has not yet indexed it in their directories.
You can check a site's Google PR here: Google PR checker.
Alexa Traffic Ranking
The ranking is done with numbers as the website with the most traffic on the Internet (currently Yahoo) would have a traffic ranking of 1 and those with very little traffic would be in the millions.
Many believe that Alexa rankings are inaccurate, but in my opinion, if your site has an Alexa PR of 100,000 and lower, this means you sure have a lot of visitors and traffic. Alexa rates your site based on the number of visitors who have their toolbar(http://www.alexa.com/siteowners/widgets) installed. That's the explanation why technology and marketing related sites have higher Alexa rankings since many of their audience are tech savvy so to speak. Alexa rankings are based on digits. 1 being the highest and it goes down to 30 million or so as lowest. For example, an Alexa rank for a new site would go to the range of 28 million or so. While a very famous site like Facebook would rank as 2.
You can go to Alexa and register your url for their indexing. It's also advised that you install their toolbar.
Recap. Though they may differ in the way they measure page rankings. They are the pioneers and leaders when in comes to determining how popular and useful your page is.
You could also view how you could increase your blog's visitors in one of my posts.
Also, if you have any questions, suggestions or any violent reactions, don't hesitate to post a comment or send us a feedback.