Thats what Jakob Neilson would have us do, if you can read all the way through the 1068 words he uses to tell us this. (Which his summary would have us believe you probably won't.)
Summary: On the average Web page, users have time to read at most 28% of the words during an average visit; 20% is more likely.
Neilson is a usability expert. This means he studies the way we use the web and he suggests ways in which we can design the sites or pages to better for users of those pages. Many of the things he talks about are relevant to my own business consulting with other small businesses and developing web sites for them. More and more, I am encouraging my small business people to take the time to write their own websites with me. If you are thinking of writing your own web pages, you may want to see this article.