Google continued to expand its share of search engine queries in the US in February, establishing a lead of almost 15 percentage points over Yahoo, according to comScore Networks.

Google processed 42.3 per cent of search engine queries in February, while Yahoo came in a distant second place with 27.6 per cent. In February 2005, Yahoo seemed to be making a run at Google, with only 5 percentage points separating them.

The share of search engine queries plays a direct role in the amount of paid search advertising revenue these vendors are able to generate.

Paid search advertising is a multi-billion-dollar market. The Interactive Advertising Bureau (IAB) estimated this month that US internet ad revenue reached $12.5 billion in 2005. Although the group didn't break out that figure into segments, typically paid search makes up about 40 per cent of total online advertising. IAB plans to report final figures and more details next month.

Yahoo has been investing heavily in developing and refining its own search technology, and in operating and growing its own paid search ad network.

Microsoft, which, like Yahoo, has invested in its own search engine and paid search ad network, came in third place and also saw its share shrink in February by almost 3 percentage points to 13.5 per cent.

Google is clearly beating both of them in user popularity in recent months. What looked like a tight race between Google and Yahoo in the first half of last year seems to be unravelling.

The trend could already be seen in November of last year, when Google nabbed almost 40 per cent of all searches in the US, more than 10 per cent over Yahoo, according to comScore.

Rounding out the top five search engines in February this year, Time Warner’s AOL took fourth place with 8 per cent, down almost 1 percentage point, and IAC/ InterActiveCorp's, formerly Ask Jeeves, took fifth place with 6 per cent, an increase of 0.7 of a percentage point.