In recent months, Google has been working on an improved version of the search service that goes by the code name Caffeine. According to Google, the new version will offer a greater number of indexed websites as well as faster and more relevant search results.
Google states that users will not see any noticeable differences compared to the current version as the big news is under the hood. In a blog post, Google invites users to test Caffeine and compare whether the search results are better than the current version of the search service.
You can find the trial version of Google Caffeine here.