He and others have been banging on about 'above the fold' for a long time now. So long that the original context of the phrase (newspapers) has probably been forgotten by many.
He's saying that visitors to a website do scroll most of the time, but the attention given to what is beyond the first viewport is significantly less than what is presented up front.
Why is this? Basically, while technology continues to move on apace, our behaviour doesn't. We're lazy, impatient and have a low attention span when it comes to interacting online.
Interesting also that the stark figures from his study are similar to those in a study done by Google on the impact of ads. There's a link to this study too.
So what do we do? Continue to follow best practice in writing for the web which has been laid out for a long time (especially in Ginny Redish's excellent book 'Letting Go of the Words')
- Meaningful page title
- A useful, concise summary of the contents of the page
- Avoid 'false bottoms' in your design (elements that give the impression you're at the foot of the page when you're not)
A couple of my previous posts related to this:
Users scroll but rarely read (April 2010)