Google was used for two thirds of all internet searches in September, says ComScore.

The research firm revealed that Google was 0.7 percent up on figures for August this year. Google seems to have increased its share at the expense of Yahoo. While Google's share increased, Yahoo's share decreased an identical 0.7 percent, from 17.4 percent to 16.7 percent.

Microsoft was in third place with 11.2 percent of searches, up from 11.1 percent in August.

Out of 16 billion "explicit core searches" – defined as "user engagement with a search service with the intent to retrieve search results" – 10.6 billion were conducted through Google.

Ask and AOL combined for about 6 percent of the search market.

Instant Search

In early September Google unveiled Instant Search, which lets users see results even before they finish typing a word. ComScore said it had to alter its measurement technique in order to account for the change, and prevent Google from artificially improving its market share.

"The page is dynamically updated as the user continues typing, which could potentially generate a large number of result pages that may or may not be of user interest," ComScore said. "Fortunately, the comScore panel provides visibility into all events that a user is conducting and all the HTTP calls associated with the user's actions."

Google's market share increase came just as Microsoft announced that it's teaming up with Facebook to make search more 'social'.

"When you search for something on Bing or in web results on Facebook (powered by Bing), you'll be able to see your friends' faces next to web pages they've liked. So, you can lean on friends to figure out the best websites for your search," Facebook official Bret Taylor said in a blog.

Bing, of course, already powers Yahoo searches, making it the most serious competitor to Google in terms of providing back-end search technology.

Bing has enjoyed a fast rise, coming online only in June 2009, replacing the previous Microsoft service known as 'Live Search'.

Despite Bing's quick start, Google's market share has remained pretty steady. Google held 65 percent of the market in May 2009, whereas Yahoo held 20 percent and Microsoft held 8 percent, according to comScore. Bing's impact has therefore been more pronounced on Yahoo's market share than on Google's.

ComScore is not the only firm analysing search share. According to Hitwise, Google did even better in September than comScore indicates. Hitwise numbers show Google increasing from 71.59 percent in August to 72.15 percent in September.

See also: Google versus Microsoft Bing