In a nutshell, Internet Explorer 4.51 includes new SSL version 3 security certificates from VeriSign. Some certificates which originally shipped with Internet Explorer 4.5 expire 01-Jan-00, at which point it becomes impossible for Explorer to establish secure connections to some Web sites (such as online merchants or financial services). Both Internet Explorer 4.51 and Outlook Express 5.01 offer improved support for version 3 certificates that should allow automatic updating in the future. Installing Explorer 4.51 is merely a matter of drag & drop in the Finder, though a few people have had troubles; see TidBITS Talk for details and fixes. Netscape browsers earlier than version 4.06 may also have the same problem with certificate expiration.