All writing is persuasion. The ancient Greeks called it rhetoric. They would get into arguments and debates just for the sake of argument- to show off their rhetorical ability.
Although your website probably isn’t facilitating some kind of verbal brawl, you want people to see things from your perspective, to agree with you or understand you. Online writing is no exception.
It is important to recognize that your goal is to persuade an audience. You want them to trust you, to agree with you. You want them to spend time on your site and return to it later.
Like an earlier post mentions, the copy (information in word form) on your site should be different than the same copy in print form. Basically, you need to cater to an internet audience with different limitations and abilities to consider.
Presentation is important. Publishing a web page is like showing up for a job interview. SEO will help determine how many “interviews” you get, but it’s the look and feel of your site that will get you the job.
People search the internet looking for something. If you play it right, your site can be just what they need- whether you are selling something, introducing an idea, or leading viewers somewhere else. A good site is viewer friendly: aesthetically appealing and simple.
Thoughtfully consider the words you use. Your language should be visual and active, but not overly descriptive.
Organize yourself and be in control of your voice. Your voice is like the tone of your writing (the way it would sound if you were saying it out loud). Give your voice a personality people can relate to; make them feel like you’re actually talking to them.
Short and sweet is best. Anyone who reads regularly from a computer screen knows that a daunting sheet of text, even when it’s broken up, can deliver up a big fat headache to the reader.