Currently, fewer than 1% of search queries are affected by the site speed signal in our implementation and the signal for site speed only applies for visitors searching in English on Google.com at this point. We launched this change a few weeks back after rigorous testing. If you haven’t seen much change to your site rankings, then this site speed change possibly did not impact your site.

According to Matt McGhee at Search Engine Land,

there are two primary ways Google will measure page speed:

1. How a page responds to Googlebot
2. Load time as measured by the Google Toolbar

You can check on your site speed in Google’s Webmaster Tools, under Labs > Site performance, and Google points to several other resources to work on your site speed:

• Page Speed, an open source Firefox/Firebug add-on that evaluates the performance of web pages and gives suggestions for improvement.
• YSlow, a free tool from Yahoo! that suggests ways to improve website speed.
• WebPagetest shows a waterfall view of your pages’ load performance plus an optimization checklist.
• Many other tools on code.google.com/speed.

Google emphasizes that page speed won’t trump actual relevance.

The next step for your website will be the need to develop a sitemap.xml file – which can be created by a WordPress plug-in, if you are using WordPress to run your website (which I highly recommend). If you have any other type of site – go to this site to have them “create yor google sitemap” free via their website. Then you add this via Google’s Webmaster program.

Now Google can update you on your website problems, including virus on your webpages, and allowing your newest blogs, posts,etc to be updated to Google asap.