Users don’t like sites that take too long to load. Site speed is a key quality, according to Google, after the results of studies of user habits. Faster loading time of pages reduces the operating costs of the Internet over a longer period and improves user experience on your website.
Faster websites make internet users happy, and when users are happy Google is happy. So Google has decided to make page load speed important factor, content and relevance of web site information are still the primary factor in Google ranking, but if your website takes to long to load it will affect your ranking. Meaning, if there are two similar websites, Google will more likely serve the faster website higher on the result page then the slower website.
From now on, an integral part of the algorithm for ranking web site to Google will include the factor of speed (among about 200 other factors). Google will use two methods to measure the response speed of presentation: speed of response to the Googlebot and the load time Google Toolbar. The new ranking system was launched a few weeks ago, where currently only 1% of search results obtained included the new rules. For now, this change does not affect much on the results but that does not mean that it will not change soon!
How to measure time your website takes to load
There are several tools that can help you measure you loading times. If you are using Firefox, and as every good web designer you have Firebug extension installed then you should add two more extensions that work as a component of Firebug. These two extensions are PageSpeed from Google and YSlow from Yahoo (of course). And there is webpagetest.org website that will give you very nice waterfall representation of your page loading.