• The browser can now be themed with Personas (lightweight themes).
  
• The bookmarks system has been reworked to use the Places framework shared with Firefox.
  
• SeaMonkey now defaults to tabbed browsing instead of opening new windows.
  
• More compatibility with Firefox' tabbrowser API.
  
• The tab bar received a visual refresh.
  
• Address book toolbars can now be customized.
  
• Find in Page now works with a toolbar instead of a modal window.
  
• Gopher support has been removed.
  
• Web developers can animate content using CSS Transitions.
  
• XPCOM registration has been changed.
  
• The W3C Indexed Database API is now available to websites.