Guardian Unlimited is still the UK's most popular newspaper website, with 2.7 million unique visitors - or one in 12 Britons active online.
But The Sun, which has held second spot in the poll all year, was pipped at the post by The Telegraph. It now boasts 2,079,000 unique users, 30,000 ahead of its tabloid rival.
The figures, which covered August, also revealed that The Telegraph has doubled its web audience during 2007. Last December, it was drawing one million users.
The Daily Mail also registered impressive online growth, jumping from 700,000 in December 2006 to 1.4 million at the end of August.
The good news for The Sun was that its website kept people reading the longest - clocking up an average visit of nearly 26 minutes per person. In comparison, visitors to Telegraph.co.uk spent 15 minutes on the site, while Guardian readers stayed 11 minutes.
Overall, 7.4 million Britons visited at least one of the 10 most popular national newspaper sites.