You are looking to keep your visitors coming to your site and also get them to return. There are a number of points you should consider when copywriting for the web.
Keep your copy short and simple
What you should remember is that unless a visitor has been directed to a particular page on a site, more often than not, they will only read 1 or 2 lines of the text. So the longer your text is, the less likely they will want to read it. So if you can, do not add any long copy to any pages where visitors are not expecting it to be.
Also, keep your copy simple. This matters as much as how long it is. It is important that your visitors are able to understand what has been written on their first reading. They do not want to have to spend time thinking about what you have written.
In most cases, you should be able to convey one key idea effectively in just one or two lines of writing. By writing any more than that, you are likely to ruin the chance of the first idea you are providing to get through to them.
So by anticipating that your visitors will be willing to learn more about something, then they will look for the page that has more copy on it. So provide them with a link to another page of your site where they can get hold of the information that they need.
What if you do need to write long copy?
If you do need to include some longer copy, then organize it. Even if your visitors are expecting to find a page heavy with text, they may not actually be willing to read it. So in order to help them, divide any distinct ideas you have into separate paragraphs. Provide them with useful headings, subheadings and bulleted lists. This is a great way of introducing key ideas to them deliberately.
It is best to assume that not all the visitors to your site will read longer pieces in their entirety. So write copy that they will be able to skim through and lets them read the parts that they are only interested in.
Although longer copy does not need as direct as the short copy is, it should still be easy to read. You will find that those visitors to your site who have difficulty understanding what has been written, will stop reading it.
Make your Copy Lively
Keep your copywriting clear and write vividly. You should be aiming to write in a light, unassuming tone of voice. If what you have written is boring or overbearing, this will, in turn, affect the reader, and what you are trying to convey will not get through to them.
So use a consistent voice throughout your copy. By doing this, visitors will more quickly recognize it and so become familiar with it. The more familiar a site or subject is to them, the more effective it will be.