Write For The Web - Designing A Readable Site
Once you've built a site which will encourage your visitors to read what you have to say, you need to check that your copy itself is likely to hook readers and keep them hooked. You will never achieve a situation where every visitor reads every article from beginning to end, but you can at least get your most important points into the majority of visitors' minds.
Keep paragraphs and articles short. Paragraphs should be no more than about five sentences, and you should roughly halve the wordcount that you would expect if you were producing the article for print.
Split up your text. Put a clear white line between your paragraphs, and use lots of subheadings and bulleted lists where appropriate. This will make it easier for visitors to scan your text and find the information they want.
Embed links in your article to other relevant pages of your website. Then, at least when they click away, they'll be clicking to more of your content.
Put the crux of your article at the top. That way, you'll have a better chance of grabbing your readers' attention by telling them exactly what you are going to talk about. You can employ this technique with paragraphs and bullet points as well: have a short sentence at the beginning which describes the point of that paragraph.
Only introduce one idea per paragraph, as people are likely to skip onto the next when they feel you've reached any sort of conclusion.