Ever since Google floated the idea of Page Rank, it has became one of the most important aspect of Search Engine Optimization. Higher Page Rank will push the position of a website towards the top in a Google search, which is the major search engine in the world. However, the information on Page Rank is scare. The only ways to view what is your website's Google Page Rank is via Google Toolbar or Google Directory. Even so, the Page Rank is not updated instantly. It's updated only once about 3 months.
SEO Company's Page Rank Update List History provides some important information on when a Page Rank update occurred, and predicts when is next. It also contains information about backlinks update, and other Google related update. Backlink is the link from other website to your website. Basically, the more quality backlinks you have, the higher the Page Rank will be. So the information of the backlinks is important too.