Netscape Navigator versions 4.05 and earlier and Microsoft Internet Explorer 4.01 and 4.5 for Macintosh include a security component that expires at the end of 1999. Please note that this is not a Year 2000 issue.
If you do nothing, you may see a warning message when accessing secure parts of the Yahoo! site after December 31, 1999. The message may state that the certificate used to protect the transmitted information has expired.
The SSL connection between the Yahoo! servers and your browser will be as secure as before. This is not a security risk.
To address this issue, you may do one of two things:
More details from Verisign.