Google is to start using page loading speeds to help rank its search results for any given search query. Google has taken this step because studies show how web users prefer visiting fast loading websites and will leave anything with a slow load time.
Google's ranking of results has always been based on a number of ever changing metrics including the relevance of the content on a webpage and number of referrering sites amongst many others - now there is one more metric to take into account when optimising your website - speed.
Despite the change, Google has explicitly stated the most important criteria for ranking results remains to be the relevance of a page to a particular query. It is though that only around 1% of search queries will actually be affected by this change. According to Google just over 1% of the total search queries will be affected by this new feature.
Currently this metric is only taken in to consideration on US search results but will be introduced in the UK within the next month or two.