Each page of your website has a Google PageRank (PR) value, and as such you can simply add up the individual PR values of each page to arrive at the total PR that your site has (Keep in mind however that someone speaks of PR, it applies to a page). How you structure your internal links can influence to some extent what the PR value of a page will be, as will external links pointing to a page on your site. Although for SEO page PR value is important, you should really be trying to increase your total site PR value.
There are only two excellent ways to increase your “site PR” value:
1. Get more incoming links that point to pages on your site.
2. Add new pages to your site (which was discussed in a previous chapter).
The actual PR value of each page indexed by Google on the Web is in constant flux. All over the Web, new pages are added, old pages are removed, more links are created – all of which over time decrease the “value” of your incoming links.
As the number of websites (and web pages) in Google’s index increases, so does the total PageRank value of the entire Web, and so also does the high end of the overall scale used. This is kind of like the top student setting the “curve” for an exam at college. The top student gets 100% and everyone else gets correspondingly less. Therefore, the top-ranking site (or handful of sites in actuality) gets the maximum, perfect PageRank score (which is a 10 in the Google Toolbar) and everyone else is scaled down accordingly. As a result, some web pages may drop in PageRank value for no apparent reason. If a page’s actual PR value was just above a division on the scale, the addition of new pages to the Web may cause the dividing line to move up the scale slightly and the page would end up just below the new division.
What this means is that you should always strive to get more links that point to your site, otherwise your site can naturally start slipping in rankings due to this decay of PageRank value for incoming links – both from other pages on your site as well as from other websites. This is also why you should add new pages to your site on a regular basis, as additional pages will increase your site’s total PR score too.