Google Toolbar PageRank Update
Matt Cutts has recently release this video of him answering a question about PageRank and why it is still being used, even though its use has become less and less relevant in recent times.
What is PageRank?
PageRank is a system which is used by Google to determine the importance of a website using this formula. As SEO's we previously placed significant importance on this, correlating site rankings with higher the PageRank number. From a metrics standpoint it doesn't really make a difference anymore but it does however contribute to your websites indexing frequency and also as a penalty indicator.
If your site has a higher PageRank Google will see this site as being more important and will be deemed worthy of more frequent crawling and will increase indexing. This means that when you add (rich and engaging) content to your site it will rank quicker on the SERPS.
Google have just carried out a PageRank refresh and Matt states that they will continue to do so as long as they see people are seeing it in their tool bars but concedes that the "writing is on the wall" in the long term. This is due to people upgrading to newer browsers, such as IE 10, which don't support the toolbar add-on, meaning this would see the PageRank toolbar be phased out over a period of time as less people were using it