US web surfers continued to flock to Google in April, using the internet search site for 50 per cent of their 5.3 billion queries.

That marked a rise from Google's year-ago market share of 47 per cent, while second-place site Yahoo held steady at 22 per cent, and MSN dropped from 12 to 11 per cent, according to Nielsen/NetRatings.

The trend mirrored an announcement Thursday that Dell had agreed to load Google software, such as its desktop search application and browser toolbar, by default on new consumer PCs at the expense of competing Microsoft products.

Google cannot sit on its lead for long, warned Michael Lanz, vice present of search industry solutions for Nielsen/NetRatings. The top search providers will continue to compete for customers' loyalty with new features, improved functionality and rewards programs.

In the past year alone, all three have succeeded in boosting their number of monthly searches. Google's search count rose 34 per cent from 1.9 billion searches in April 2005 to 2.6 billion in April 2006. Yahoo rose 27 per cent from 919 million to 1.1 billion, and MSN rose 10 per cent from 515 million to 570 million.

Those numbers can translate into revenue as increased traffic allows each search company to charge a higher rate for more exposure of clients' advertisements.

Allen Weiner, an analyst with Gartner, observed that search providers are moving from a "straight search" method based on algorithms and page rankings to a "social search" method that incorporates human knowledge and other people's preferences.

Yahoo has made the most progress, with its Yahoo Answers site already running, while Google has lagged with its Google co-op site still ramping up. Yahoo also has an advantage in worldwide traffic, with a greater Web presence outside the US than Google does, Weiner said.

Meanwhile, Google will rely on sheer numbers to preserve its advantage. "These three guys are like the three TV networks back in the old days, and right now, Google has the top ranking show. Until proven otherwise, they're the leader," he said.