Here are some general rules.
If you are selling one product or service on your website use long copy on your homepage.
If you are selling more than one product or service on your website – use short copy on your homepage. Highlight a couple of key products or services. Spark people’s interest and then direct them through to a page of long copy.
Use short copy if you are ever presenting a list of products or services on a single page (i.e. a category page). Use the short copy to direct the visitor through to a page of long copy.
Use long copy on any page focused on a single product or service whenever possible. Provide your visitors with as much information as possible.
As with all rules … sometimes the rules don’t apply. But if you are going to break the rules then you should have a good reason, and your reasons should be backed up by some solid evidence that you have obtained from careful testing.
So, let’s look at the process of writing effective long sales copy for the Web.