Symantec was founded in 1982 and is the leading company in SSL certificates. It is the biggest software company in the world with over 18,000 employees spread across 50 countries. Symantec used to be called Verisign and the brand is now called Symantec SSL Certificates. With this company being responsible for many types of high quality security measures such as the Norton Secured seal and malware scanning, they are certainly a company that you can trust. It is likely that your customers will have heard of them as well and will also trust them. The company is known for its quality and have great customer support which means that if you have any problems, you will get the help that you need.
Symantec provide a big range of different SSL certificates. This means that whether you want just basic protection or something very secure for many domain names, they will have a solution for you. Many large companies and banks use Symantec to keep their systems secure and therefore you will find that their security measures can be trusted. You may find that they are the security company that your customers have heard of and this will mean that if you display their security seal, then customers will know that your site can be trusted too.