Opera  10.50 Beta 1 (Build 3247)

# New features

* Better integration with the Windows operating system

Windows 7:
- Aero Glass
- Aero Peek
- Jumplists

* Opera Carakan JavaScript engine
- Cross-platform bytecode interpreter for a new register-based instruction set
- Internal object model with automatic classification and inline property caching
- Machine code generation (JIT compiler)
- Divided garbage collection heap: automatically traverses the memory of active heaps
- Caching of compiled programs
- Reduced memory usage
- Further Carakan information (http://my.opera.com/core/blog/2009/12/22/carakan-revisited)

* Opera "O" tab and menu
The new Opera "O" tab and its associated menu (located on the left side of the Opera Tab bar) replaces the traditional Opera Menu bar. This increases vertical space in the Opera desktop window, and centralizes frequently used features and tools in one, convenient location. Optionally, the new Opera "O" tab and menu can be replaced with the traditional Opera Menu bar by clicking "Show Menu Bar" in the Opera "O" menu. This new Opera feature contains the following items.
- Tabs and Windows
- Page Tools
- Print
- Bookmarks
- History
- Downloads
- Opera Unite
- Synchronize Opera
- Widgets
- Notes
- Mail and Chat Accounts
- Mail
- Contacts
- Appearance
- Settings
- Help
- Show Menu Bar
- Exit

* Opera Presto 2.5 rendering engine
The Opera Presto 2.5 rendering engine includes the following additions and improvements.

CSS
- CSS 2.1 visibility: collapse
- CSS3 border-radius property (rounded corners)
- CSS3 Backgrounds and Borders
- CSS3 2D Transforms
- CSS3 Transitions
HTML
- HTML 5