Mozilla has published an official feature list for Firefox 3.6 in the form of a guide for programmers who need to know about the changes. The Firefox 3.6 developer guide mentions an ability to automatically hide the menu bar, a change that dovetails with sparer Firefox user interface designs that Mozilla has begun exploring for Firefox versions 3.7 and 4.0. That's important for plug-in developers and others who use the menu bar to control their add-ons. For those developing Web applications, there's a feature for adding sounds that can play in response to specific events. Eric Shepherd, who oversees Mozilla documentation work, called the plans just an initial sketch, so don't consider this the final word on Firefox 3.6 features.