ising , ▁adding ▁complete ▁brand ing ▁messages ▁and ▁contact ▁information ▁in ▁a ▁display ▁ad ▁is ▁prohib itive ▁because ▁then ▁a ▁click ▁through ▁to ▁a ▁website ▁is ▁not ▁necessary . ▁ 2 4 . ▁All ▁parties ▁involved ▁see ▁different ▁impress ions ▁reports ▁that ▁are ▁impossible ▁to ▁recon cile . ▁ 2 5 . ▁Report ing ▁laten cy . ▁Because ▁server ▁log ▁files ▁must ▁be ▁batch ed , ▁filtered , ▁and ▁transferred ▁to ▁a ▁database ▁for ▁reporting , ▁significant ▁del ays ▁exist ▁before ▁reporting ▁data ▁is ▁available . ▁ 2 6 . ▁No ▁reported ▁log ▁or ▁visual ▁representation ▁of ▁each ▁unique ▁vie wer ' s ▁environment , ▁including ▁vie wer ' s ▁display ▁resolution , ▁and ▁browser ▁window ▁area ▁and ▁scrolling ▁position ; ▁ 2 7 . ▁No ▁reported ▁log ▁or ▁visual ▁representation ▁of ▁each ▁web ▁page ▁URL ▁an ▁ad ▁is ▁delivered ▁to ▁in ▁addition ▁to ▁the ▁web ▁page ▁dimensions ▁and ▁pla cement ▁location ▁of ▁the ▁ad ▁on ▁the ▁web ▁page . ▁ 2 8 . ▁No ▁data ▁reported ▁for ▁the ▁view ▁time ▁of ▁each ▁individual ▁view able ▁impression . ▁ 2 9 . ▁C PM ▁value ▁dil ution ▁because ▁of ▁an ▁un limited ▁supply ▁of ▁invent ory . ▁ 3 0 . ▁Red und ant ▁ad ▁delivery . ▁( The ▁delivery ▁of ▁the ▁same ▁ad s ▁on ▁the ▁same ▁web ▁page .) ▁ ▁See ▁also ▁ ▁Click - through ▁rate ▁ ▁View - through ▁rate ▁ ▁Comp ens ation ▁methods ▁ ▁Cost ▁per ▁action ▁ ▁Cost ▁per ▁click ▁ ▁Cost ▁per ▁m ille ▁