Last week Google updated the PageRank values that it shows in the Google Toolbar. The new PageRank values should be visible at most Google data centers, but it might take some time before the measures are changed at all DCs.
The search engine changes the ranks of a page every 3 or 4 months and makes them available in the toolbar. In his blog, Matt Cutts of Google explained that, "PageRank is computed continuously; there are machines that take
inputs to the PageRank algorithm at Google and compute the resulting
PageRanks. So at any given time, a url in Google’s system has
up-to-date PageRank as a result of running the computation with the
inputs to the algorithm. From time-to-time, that internal PageRank
value is exported so that it’s visible to Google Toolbar users."
PageRank is Google's system for ranking web pages. It indicates a page's value by analyzing the links a page receives and the value of these links. In giving a certain rank to a page Google also considers the number of times a keyword appears in that page and examines the page's overall content.