As promised, Mozilla released the fourth beta of Firefox 4, bringing a few new features while stabilizing other parts as well. Development may not go as fast as some would have liked, but Mozilla seems focused on getting the right features in.

• Firefox 4 Beta 4 is available in 39 languages.
• Firefox Sync is now included by default.
• Users can organize their tabs using Firefox Overview.
• An experimental API is included to provide more efficient Javascript animations.
• Firefox now supports the HTML5 video "buffered" property.
• See the complete changelist from the previous beta.

As always the full binary download is available, existing beta users will receive the update automatically (or by triggering it from the Help menu). Good luck with hunting bugs!