The good news is that prospects are using your web site to research your company and products. But they're likely to be early in their buying cycle. There's no guarantee they will ever be back. Most of them won't remember your web site at all a few days later.
Your challenge is to capture their contact information (especially their email address) while they are on your web site for the first time--to get permission to send more information. Don't make them leave your web site to get it. You can then implement an automated process to follow periodically by email, providing more information and building a relationship over time--until they're ready to buy.
Your web designer should work to create a direct response model that focuses solely on capturing leads. More prospects will buy after they visit your site--if you capture their information while you have the first chance.