Many merchants focus on their catalogs and ignore the additional content that their sites require to build trust with their customers and increase their conversion rates.
Below is my list of pages and content that every eCommerce site should have.
1) Contact Us: Include a local and Toll Free number, hours, email and if possible an address. If you are a home based business and don't want someone showing up or Google Streetviewing your front porch, then include a box number at your local post office.
2) About Us: A bit of history or story can help. They just found you online from the other side of the country, they don't know that you have had a physical store for 20 years
3) Returns & Exchange Policy: People want to know that if there is a problem, you will deal with it.
4) Shipping Rates & Policies: Don't leave this as a surprise in the checkout. Post it prominently. "Orders received before 2pm are shipped the same day" and similar information sets peoples mind at ease and can set reasonable expectations.
5) Privacy Policy: This is serious business. We stopped giving customers templated Privacy Policies since we discovered that some of them were not reading it, then playing fast and loose with their commitments. Read what others are saying and create your own.
6) Terms & Conditions: This is an interesting one a lawyer brought up the other day. Specify the jurisdiction that governs your primary business and that you are not responsible for bad things that could happen because of the customers choices.
7) Security Policy: This can be combined with Privacy and can also be replaced with secure site seals from TrustWave and your SSL provider.
8) News/Press/Media: This helps to reinforce the legitimacy of your business and builds trust. Keep it current.
9) Store Locator: If you manufacture a product or run a chain of stores this is crucial. Studies show that people pre-shop on the web all the time.
That should be enough to convince anyone that your business is legitimate and should increase your conversion rates.