Mail Online surpassed Telegraph.co.uk and Guardian.co.uk in May to become most popular national newspaper website in the UK, with 18.7 million unique users, the Guardian reported Thursday.

The Daily Mail & General Trust's site network in May achieved its highest unique user number on record with 100 percent year-on-year traffic growth, according to the latest Audit Bureau of Circulation figures published Thursday.

Mail Online had over 18 million global unique users during May, up 100 percent from May 2007 and 3.7 percent compared to April. Page impressions, however, dropped slightly from April to about 138 million.

Both Telegraph.co.uk and guardian.co.uk have its traffic down from April. Telegraph.co.uk slipped by 0.8 percent to about 18.5 million unique visitors in May, but its year-on-year user figure was up 154 percent compared to May 2007. Page impressions reached their highest at about 136.8 million last month, the Guardian reported.

Guardian.co.uk marked a month-on-month unique user decline of 1.2 percent to 18.3 million, while its Year-on-year users up 14.1 percent. More than 178.8 pages were viewed last month.

In terms of the unique visitors from the UK only, the most valuable audience for advertisers who focus mostly on domestic campaigns, Guardian.co.uk was still on the top. It had over 7.6 million British users in May, or 41.8 percent of its overall online audience, according to the Guardian.

Telegraph.co.uk recorded 6.1 million British unique users last month, or 32.8 percent of its audience, while Times Online saw 35.7 percent of its audience or about 5.7 million users coming from the UK.

Sun Online had 34.3 percent of its total traffic from the UK, or 5.1 million unique users, and Mirror Group Digital had 2.6 million, or 53.8 percent.

Mail Online had nearly 5.1 million UK users last month, or 27.2 percent of overall audience, according to the Guardian.