Writing for the Web
Tests have shown that the speed for reading on screen is 20 - 30% slower than it is for print and the reader reads with less concentration and accuracy.
When users are tested via eye tracking it shows that they scan down a page rather than reading from top to bottom.
Your audience wants to find information quickly and expects it to be easy to read. In order to keep your audience’s attention you need to keep it short and stick to the point, make the copy easy to scan by using frequent sub headings and lists.
Keep Them Reading
It goes without saying that your copy should be geared towards your target audience's level of understanding, interest and technology skills.
Have someone proof read all of your copy. You are too close to your work, you know what it is you are trying to say but have you really said it. Nothing breaks concentration more than having to keep rereading trying to understand the meaning. Also they can check for any grammar and spelling errors you might have missed.