Most of you are probably saying - of course we all read on the Web. This may be true for some of you. But the correct answer is - few people read while they are on the Web.
If we are not reading, then just what are we doing? Scanning.
This phenomenon was discerned in the early days of the Web and there were many formal studies performed by various educational institutions and scholars.
Anyone who has reached the age of 40 and discovered that overnight their arms have gotten shorter and they can't hold the book far enough away to see the print, will also tell you about their struggles to read from the screen.
Most of us experience reading a screen as being more difficult on the eyes than reading from a printed page. The eyes tire easily, get dry, look red and feel sore. We compensate for the discomfort by scanning the page to get directly to what we want and often ignore what might be useful. Our eyes are always drawn to bullet points on a page as they seemingly "pop" from the page and are easy to scan.
I have also experienced this issue from the accessibility side. While setting up computers for low vision users, I learned how difficult it can be for a person with low vision who is using screen magnifying software to read from a non-accessible Web site. The eye struggles to find its way back from the end of the line to the beginning of the next line.
In order to aid all users, we advise our Web site clients to keep all sentences simple, all paragraphs short, to use meaningful sub-headers and bullet points whenever possible.
To promote reading on the web and support the technology of accessibility, use structured headers for organization, legibility and usability.