Firefox 3 is to support SQLite for offline storage. The new alpha release tells us this and a lot more (below).

The world of the RDBMS has come to the browser, and has jumped from server to client in the Web platform.

• Bookmarks portion of Places has been enabled
• New crash reporting system, Breakpad. It’s
  enabled by default on Mac OS X, on about 50% of Windows installations, and not yet available on Linux.
  You can also view crash reports at this site.
• New Javascript-based Password Manager. More details available here.
• Support for Growl notification under Mac OS X
• Support for native controls on Mac OS X
• Miscellaneous Gecko 1.9 bug fixes

Source:? ajaxian

Mozilla, Firefox 3, Alpha, SQLite