Inc. Magazine has a great article posted called Turning Browser Into Buyers. One of the biggest nuggets of wisdom in the article: In addition to having a clear message about what you're promoting, you've got to have a Call to Action on your website. What is it that you want the visitor to do? Buy a product? Visit a meeting? Make a phone call?

In the example they give, Stamps.com originally had a small "Sign Up" button -- which is vague and brings to mind filling out lengthy forms. Bleh. Their revised site now features a large red button at the bottom of the page that says, "Get Postage!" The call to action is clear -- "This is why you are on my site, and this is what I want you to do!"

Be sure that you have communicated clearly to the users what their part is.