BBB Seal –
The Better Business Bureau has been around for a long time. If you have not registered with them then it is highly advisable to look into it. Rates vary, but overall it is pretty inexpensive. This is a common logo that many web goers look for when purchasing online. Contact your local BBB for more info.
SSL Seal –
Examples of this are Verisign, and Equifax (now known as Geotrust). Both companies offer a seal that shows your company is using Secure Socket Layers. SSL is a cryptographic protocol which provides secure communications on the web for such things as email, and order placement as well as a pleura of other data transfers. Critical for any legitimate ebusiness.
100% Guarantees –
This is typically marketing speak that helps reassure to the user that you stand behind what you sell. This sort of thing can vary from company to company, but helps instill confidence in the buyer.