Server certificates are presented to the browser the first time a secure connection is established. At that point the browser needs to decide whether or noth it trusts this secure web server.  The browser has a list of trusted Certifying Authorities, and it checks the signature on the server certificate against that list.  If the browser does not know about the CA that signed your server cert it will warn the user, and possibly refuse to connect.

Some browsers may let you connect anyway, or they may allow you to add the CA to the list of supported and trusted CA's.  Very old browsers cannot have new trusted CA's added by the user.

Thawte's server certificates are trusted by more than 97.5% of all the browsers in active use for electronic commerce, and we expect the release of 4.0 generation to take that figure over 99%.  Here is a full map of the browsers that work with our certificates. The colour coding tells you if the browser will work out of the box, if it can have the root manually inserted, or if it's beyond hope.

If your browser falls into the "Installable" category then click on the link, open the file and accept our cert as a new root authority.  However, if you are running MSIE 3.0, seriously consider updating either to 3.02 ( a small update) or to 4.x or later because 3.0 has a major security hole that allows any webmaster to take control of your desktop - including accessing any confidential files on your PC.

Netscape Navigator 3.x You need to delete the old root, and install the new one. Choose Options, Security Preferences.  Find the entry marked "Thawte Server CA".  Delete that certificate.  Now point your browser at http://www.thawte.com/serverbasic.crt and accept the new root certificate.  This certificate is identical to the last one, except that it is valid till 2020 and is the same as the certificate in Communicator 4.x.

Microsoft Internet Explorer 3.x This only works on IE 3.x on Windows95 or NT 4.0. Choose View, Options, Security, Sites.  Look for the entry called "Thawte Server CA".  It may or may not be there, depending on your precise browser version and upgrade history.  If it is there, click on it, then click on "Delete".  Click on OK.  Now point your browser at http://www.thawte.com/serverbasic.crt. Choose "Accept and Enable" and press OK. Restart your browser.  You should now have a "Thawte Server CA" entry that is valid till 2020