A trust seal is a seal granted by an entity to website or businesses for display. Often the purpose is demonstrate to customers that this business is concerned with security and their business identity. The requirements for the displaying merchant vary, but typically involve a dedication to good security practices or the use of secure methods for transactions or most importantly verified existence of the company. Trust seals can come in a variety of forms, including data security seals, business verified seals and privacy seals and are available from a variety of companies, for a fee. A Trust seal can be either active or passive. Most seals are validated when they are created and remain so for a specific duration of time, post expiry of which the business/process has to be re-validated. (Source: Wikipedia)
A Trust Seal is a good idea for any web site for many reasons. The most important reason is that the web site is trusted by a 3rd party. The bad thing is, who is trusting the third party ? If the Trust Seal is provided by a well known company such as Norton, McAfee, Etrust, or Trust Guard then it's probably pretty reliable, however you are going to pay a premium price for a Trust Seal provided by these companies. Beware of any lesser known company who is charging you for a Trust Seal, how do you know that you can trust them ?
With that said, there is a way to get a Free Trust Seal that is backed by Google, Norton, McAfee & Sophos that is provided by a service called asafesite.com however you are going to see some ads on the results page that is displayed after clicking on your trust seal.
One final word. Steer Clear of MyWot which offers Trust Seals & Web Site Reviews but is populated by a community of users who thrive on giving web sites bad reviews en masse hoping that they will buy a Wot Trust Seal to better their reviews. It is a total scam no and one takes MyWot reviews seriously anymore anyhow.
Your best bet is to stick with one of the major Trust Seal providers like Trust-Guard (10% discount) if you can afford it otherwise try out asafesite.com