However, users have reported problems with the chat dropping out for periods of time or simply not working at all. Facebook has been working hard to correct these issues, apparently with much success. However, there is one caveat:
The biggest improvements come from changes that aren’t supported on older web browsers. After evaluating the alternatives, we’ve decided to make rapid improvements and provide the best Chat experience possible, which means we will no longer support Internet Explorer 6 browsers.
The end to support won’t go in effect until September 15th, in order to give people time to prepare.