Some products are easier to sell online than others. Take books for example, Amazon is doing a magnificent job in cornering that market, and that is partly down to the nature of books. They are easy to store, easy to ship and most people who buy books will come back and buy some more. Other products are a bit harder. Try selling the diet pill Anoretix for example. First of all, selling pharmaceuticals is much harder than shipping books, the legislation can be a nightmare and maintaining credibility is critical to providing a steady stream of sales.
Take Stratavia for example, a company that provides a data center automation offering. Their website offers a cohesive message around what the company does and reinforces that by promoting different ideas to improve credibility; a list of awards they have achieved, different news and quotes from their customer. All this helps sustain the image they are trying to project and strengthens their online presence.