Usability guru, Jacob Nielsen is currently on a world tour confirming results that were confirmed last year and the year before that: That people of left-to-right-top-to-bottom-reading cultures actually prefer to read Web content left-to-right and top-to-bottom. His groundbreaking research has also determined that most users are generally blind to old-school, graphical banner ads…they just don’t notice them anymore. They scan pages quickly, in an “F” pattern, looking for the juicy bits.
A less sarcastic report on eye tracking can be found here: http://blogs.zdnet.com/BTL/?p=2776
Many visitors gradually lose interest while reading Web pages because (a) they have short attention spans, (b) they don’t have a lot of time/have other things competing for their attention, and (c) the content they are reading just sucks in general.
Bottom line advice: Make your headline count. Make your first sentence count. Make your first paragraph count. Make your content interesting. If you are a Google adWords advertiser, make sure you are in one of the top 4 positions in your space (the first 2 spots above the organic listings, and first 2 spots on the top right column). And forget banner ads, they are invisible.