Content & Copy
There are loads of books (good, bad and indifferent) on copy writing. Many of the traditionally accepted rules and guidelines can be translated to the web and some cannot. What you do need to know is that COPY and CONTENT are not considered to be the same things on the web.
CONTENT is simply information. The purpose of content is to answer the need of most of the people most of the time - information. Information is the number one reason that you, your clients and customers and I go to the web. So, content is king! But if content is King, then Copy is Queen.
COPY is information that persuades your website visitors to do something - sign up for your newsletter, buy your products, contact you, etc... "Good" copy looks a lot like classic content, but if it is written well it will increase the responses that you get from your website.
If this sounds subtle and a little confusing - then you are right with me.