A certificate signer is a third party that issues digital certificates. Netscape and Microsoft browsers have built-in lists of certificate signers that they accept for online transactions.

• Netscape Navigator 3
• Netscape Communicator 4
• Microsoft Internet Explorer 4
• Microsoft Internet Explorer 5

Note that a certificate is only as reliable as the certificate signer that issued it. There is no absolute list of which certificate signers are reliable, but the ones included in Netscape and Microsoft browsers have been accepted as dependable by Netscape and Microsoft.

If you connect with a secure site authorized by a certificate signer not listed in your browser's list, you will be alerted and asked if you want to add the new certificate signer to your browser's list. It is not recommended that you add a new certificate signer to your list, unless you have a good reason to trust the certificate signer. A certificate signer does not check or guarantee the financial soundness of a company.

Related issues about security and online shopping:

What is a digital certificate?
How do I obtain my own certificate?
Is it safe to use my credit card over the Internet?
How can I tell if I have a secure link?
Basic tips on surfing securely

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