Web history is tied to the Google Toolbar. The Google Toolbar -- first released back in December 2000 -- has long had the ability to track whatever a user views across the web. This only happened if the toolbar's PageRank meter was enabled. By default, the PageRank meter was NOT switched on. In fact, it's long been joked that the relatively few people who do turn it on are SEOs who obsess over getting links from pages with high PageRank.

That's now changing. If you download the Google Toolbar directly from the Google Toolbar page, it will still be the case that the PageRank meter will NOT be switched on. However, Google will now begin prompting users in various ways to download a version where the PageRank tracking feature IS switched on or to get those with the toolbar already installed to switch it over.

LONG article by Danny