Since Google announced last year that website performance will be one (of the many) factors in determining search-rankings many of us have been paying close(r) attention to how fast our site is and even closer attention to the Site Performance graph in the Labs section of Google Webmaster Tools.

It can be quite a shock to find your site drifting into the “slow” range on the Webmaster Tools Site Performance Graph – luckily, this is usually very easy to correct, while at the same time proving that Google still needs to do some work on how this whole site performance overview works.

According to Google, it collects your website performance rating data that it uses for the Webmaster Tools Site Performance Overview/Graph from the Google toolbar:

Page load time is the total time from the moment the user clicks on a link to your page until the time the entire page is loaded and displayed in a browser. It is collected directly from users who have installed the Google Toolbar and have enabled the optional PageRank feature.

Note that Google only gathers the performance data from web-browsers with the toolbar installed AND with the Page Rank feature enabled. Since the number of internet users that has the PageRank bar enabled is probably very low, it is a trivial task to improve your webmaster tool site performance rating simply by installing the toolbar yourself, activating the PageRank bar and browsing your site (a lot) – something you probably do anyway. Of course, you DO want to optimize your site and make sure it is running as fast as possible, but you can improve your Webmaster tools performance rating even more by making sure your internet connection is fast, increase your ‘network.http.max-persistent-connections-per-server‘ to 10 or 12 (if you use Firefox) and disabling your Google Toolbar before running any scripts on your site that take long to run such as your cron.php or “available updates” update (for Drupal sites). Basically, do everything you can to make sure your website pages load as fast as possible on your PC, and disable the Google Toolbar before you do anything on your website that you know will take a long time to load. You can monitor the actual load times by using Firebug and even get hints about how to improve performance by using the PageSpeed plugin with Firebug.

To prove that I’m not just talking out of the back of my neck, I actually did an experiment. In November I un-installed my Google Toolbar, then after a few weeks I re-installed it. I monitored all of my sites in Webmaster tools, and they all showed virtually the same result:

Remember, your website-speed is one of, if not the smallest factors that Google uses to determine search-result rankings so don’t think you can “game” Google this way, but it is a good idea to keep your site running as fast as you can, and to provide that feedback to Google by enabling your Google Toolbar and Page Rank bar.