This little but very helpful sentence is the essence of everything that can be said about writing for the web.
I got aware of this for the first time during my virtual css-training “Little boxes” by Peter Müller. He uses this sentence to explain the possibilities and limits of webdesign depending on screen sizes, browsers, browser versions or individual settings.
The same can be said for writing texts for the web too. Writing a text for the web is not the same as writing a text meant to be printed on paper.
The web is not paper!
About content
The main points about content on the web are similar to the main points in journalistic writing:
The first rule you learn as a journalist is: “Write for idiots”. This means that you should build up your texts in a way that everybody – no matter if they know what you are talking about or not – will be able to follow.
Make sure to structure your text in a reasonable way. Start with the most important thing. What is the message?
This also includes being clear in what you say. Don’t babble! Especially if you want to convince/inform others about a subject.
But now comes the essential of the web: For things that can be said in addition to your main issue provide links from your main text. No matter if they lead to other websites or to another page of your own one (you can specify this in the link’s title tag btw.).
Links give the readers the choice to go into the detail or to go straight on with the main subject.
About length
Being clear and structured will also lead to shorter texts or at least shorter paragraphs. This is much more convenient for the eye too. A screen is not paper either.
And if you have a long text to publish on the web, then provide a good print version of your text. All you need is an adjusted print-css. As for texts meant for download: provide a pdf-version.
About form
“The web is not paper”. This also has consequences on the form.
It’s not enoguh to use shorter paragraphs. You should also highlight keywords (bold, italic or other color) and provide subheadlines to help the readers find their way.
As for the actual writing itself I am a fan of the puristic way:
- “font-family: sans-serif” and “font-style: normal” for continous text
- “font-family: serif” for headlines, not for continous text
- “font-style: italic“ for emphasizing or headlines, not for continous text
- underline links to make them stand out
- provide alternative texts for images
- provide title tags for links (and for images if you have no image text)
There is much more that could be said about this subject… About the differences between writing for websites, blogs or writing comments too. But this would lead too far now.
Remember: This is web, not paper! 
