Although there are significant differences among the various types of online communication, there all have one critical thing in common - they're read off a screen. There are substantial benefits, too, in that while your message is on someone's screen usually it has their undivided attention. You are genuinely "one-to-one" with them and that's something you must respect - you are literally "in their face" and encroaching on very personal territory. The bad news about online communications is that your message can be "disappeared" faster from a screen than with any other medium.
There are a few more stark facts about online communications that significantly influence how your message is received. One, according to the world-acclaimed web expert Dr Jakob Nielsen, is that 79% of online readers don't read - they scan. That's a little like the way people browse through brochures. What it means is that your message must be delivered in a way that allows key points - and benefits, of course - to be picked up at the same speed as readers scroll and scan.
Secondly, Dr Nielsen has also calculated that when people read from a screen they do so at a rate 25% slower than they read print on a paper page. That's because, despite high-resolution screens and all the other technological wizardry, on-screen text is harder to read. For this reason your messages have to be very much more concise than they do for printed media - some experts say screen text should be just half the length of its paper equivalent. In my view, therefore, there are two very important things you have to remember if you're going to get the best out of online text.
Firstly, go with the flow of the physical restrictions and write so you minimize their effect. Also, create your text so it works well for scanners (human scanners that is) by highlighting key points in bold - not italics or underline because people think those are links. That way people get the gist of your message while scrolling, although of course they will stop and read more carefully when an emboldened section really does catch their eye.
Secondly, bear in mind that even in its short little life the internet has already started to put its early folklore on a nostalgic pedestal and this plays a key role in determining what works online now. Having begun its days as an electronic kaff