Copywriting for the web is extraordinarily different from writing for offline or print media, to be precise. The prime difference is largely owing to the behavioral pattern of the average reader on the web.
An Internet user gets a torrent of options to choose from while looking for some information on the web. You type a query on a search engine, and you will see so many results on Google containing the information you want. And subsequently, you skim and scan before you get the website that has the information you were looking for.
So, now the question arises,
How do you arrive at the right website?
What makes you want to click a certain website and read the content?
What compels you to read?
You click on it because it is written in a clear, concise and interesting manner.