But don_t blame Y2K: Digital certificates set to expire.

Millions of people using older versions of Netscape and Microsoft Web browsers may not be able to access some personal finance and e-commerce sites starting Jan.1. It won_t be due to the dreaded Y2K bug. Instead, it_s because electronic credentials embedded in browsers are set to expire on Dec. 31 at midnight. These ``digital certificates'' are built into individual browsers and issued by Mountain View-based VeriSign to about 150,000 commerce and finance sites. They_re used to ensure secure transactions by verifying that both the site and user are who they say they are. The expiration of certificates could affect users of Netscape browser versions 4.05 and earlier, and Macintosh users who downloaded Microsoft_s Internet Explorer 4.5 and Outlook Express 5 before Dec. 21. To fix the problem, users need to download the latest versions of Netscape or Internet Explorer. About 5 million to 10 million Netscape users will be affected, said Chris Saito, Netscape_s senior director of product marketing. About 2.1 million Macintosh users who have Microsoft_s Internet Explorer 4.5 will also be affected. When those users visit any one of the 150,000 sites, they will receive a warning to upgrade their browser or be blocked from accessing the site until they upgrade their browser. Microsoft, which is scrambling to notify users, said it won_t be able to guarantee that transactions conducted using the older browsers will be secure. For its part, Netscape is also urging users to upgrade their browsers, Saito of Netscape said. Other sites are posting reminders. Ben Golub, VeriSign_s director of Internet marketing and sales, said the Dec. 31 expiration date was chosen about five years ago because at the time browsers couldn_t accept dates beyond 1999.