Every national newspaper website audited by ABC saw traffic fall in September, according to the latest figures.
The Mirror suffered the worst month-on-month drop with average monthly browsers dipping 15.7 per cent to 12,583,500, followed by Mail Online's 9.8 per cent fall to 67,606,156.
Most websites had a spike in traffic in August as a result of the London riots.
The Guardian had the strongest year-on-year performance with a 44.8 increase in average monthly users to 52,086,069.
Mail Online continues to be by far the most popular UK national newspaper website with 67.6m global unique browsers a month, down from 75m in August and a peak of 77.3m in May.
Full breakdown of UK national newspaper website 'unique browsers' for August 2011, according to ABC
Average monthly global browsers in September and year-on-year percentage change (month-on-month percentage change)
Mai lOnline : 67,606,156 ; 44.12 (-9.8)
guardian.co.uk : 52,086,069 ; 44.78 (NA)
The Independent : 14,675,273 ; 21.99 (-0.6)
Mirror Group Digital : 12,583,500 ; 11.58 (-15.7)
Telegraph : 37,977,383 ; 18.65 (-7.21)
Average daily browsers in September and year-on-year percentage change (month-on-month percentage change)
MailOnline : 4,063,480 ; 52.17 (-7.7)
guardian.co.uk : 2,918,571 ; 43.17 (-4.6)
The Independent : 658,113 ; 18.88 (1)
Mirror Group Digital : 606,268 ; 15.28 (-15.3)
Telegraph : 1,994,145 ; 19.43 (-7.3)