▁of ▁categories ▁de emed ▁suitable ▁for ▁that ▁age ▁group . ▁ ▁Internet ▁Watch ▁Foundation ▁ ▁Introduction ▁▁ ▁Between ▁ 2 0 0 4 ▁and ▁ 2 0 0 6 , ▁B T ▁Group ▁introduced ▁its ▁C lean feed ▁content ▁blocking ▁system ▁technology ▁to ▁implement ▁' section ▁ 9 7 A ' ▁orders . ▁B T ▁sp okes man ▁Jon ▁Carter ▁described ▁C lean feed ' s ▁function ▁as ▁" to ▁block ▁access ▁to ▁illegal ▁Web ▁sites ▁that ▁are ▁listed ▁by ▁the ▁Internet ▁Watch ▁Foundation ", ▁and ▁described ▁it ▁as ▁essentially ▁a ▁server ▁hosting ▁a ▁filter ▁that ▁checked ▁requested ▁URLs ▁for ▁Web ▁sites ▁on ▁the ▁I WF ▁list , ▁and ▁returning ▁an ▁error ▁message ▁of ▁" Web ▁site ▁not ▁found " ▁for ▁positive ▁matches . ▁C lean feed ▁is ▁a ▁silent ▁content ▁filtering ▁system , ▁which ▁means ▁that ▁Internet ▁users ▁cannot ▁as certain ▁whether ▁they ▁are ▁being ▁reg ulated ▁by ▁C lean feed , ▁experien cing ▁connection ▁fail ures , ▁or ▁if ▁the ▁page ▁really ▁does ▁not ▁exist . ▁The ▁proportion ▁of ▁Internet ▁service ▁prov iders ▁using ▁C lean feed ▁by ▁the ▁beginning ▁of ▁ 2 0 0 6 ▁was ▁ 8 0 % ▁and ▁this ▁rose ▁to ▁ 9 5 % ▁by ▁the ▁middle ▁of ▁ 2 0 0 8 . ▁In ▁February ▁ 2 0 0 9 , ▁the ▁Government ▁said ▁that ▁it ▁was ▁looking ▁at ▁ways ▁to ▁cover ▁the ▁final ▁ 5 %. ▁ ▁According ▁to ▁a ▁small - sample ▁survey ▁conducted ▁in ▁ 2 0 0 8 ▁by ▁Nik ola