We plan to begin phasing out support of these older browsers on the Google Docs suite and the Google Sites editor on March 1, 2010. After that point, certain functionality within these applications may have higher latency and may not work correctly in these older browsers. Later in 2010, we will start to phase out support for these browsers for Google Mail and Google Calendar.
Google Apps will continue to support Internet Explorer 7.0 and above, Firefox 3.0 and above, Google Chrome 4.0 and above, and Safari 3.0 and above.
Starting this week, users on these older browsers will see a message in Google Docs and the Google Sites editor explaining this change and asking them to upgrade their browser."
Excerpt from Google app team email.