Reading on the internet is like zapping on tv. If the reader does not get drawn into the text he's gone. Preparation is the key
Setting up a good page structure for the message we want to send, choosing the right level of condensation of text, presenting it in the right tone and support by the media must all be coordinated in a way your customer keeps on reading.
It's good to keep in mind what the user wants to read, and that there are some psychological tricks for convincing the user.
But not all writing for the web is content, there are menu's, labels buttons, links, images, helptexts etc. All these small items have an imense value for helping the customer to get to the conversion stage. And they can also convey your message.