New branding, standards compliant templating and accessibility improvements.

TYPO3  Version 4.0 launched

USABILITY IMPROVEMENTS IN THE BACK END

• Pages can be moved by drag and drop within the page tree in the Backend. The same is possible for folders in the filelist module.
• The context menus in the Backend opens much faster now (implemented with AJAX).
• Fixed fonts are used in the Backend configuration (i.e. TypoScript setup field or TSConfig fields) for increased readability.
• Tab indenting in Backend configuration fields (i.e. TypoScript setup field or TSConfig fields) for enhanced layout is now possible.
• The content element wizard got some improvements. Empty categories (i.e. for Plugins) are removed if a Backend user has no right to create them.
• The RTE wizard has now a save-and-close button.
• User admin module: You can switch back to admin user after user switch (SU-mode). It is now possible to create an new user in the user admin module.
• Files can be created or uploaded with buttons in the Web>List content frame.
• The admin panel uses HTTP GET instead of POST (no more browser warnings when reloading a previewed page).

ACCESSIBILITY
TYPO3's output is now valid XHTML (the conforming DTD is configurable)

The overall DTD and the XHTML-DTD may be set independently (TypoScript config.docytpe and config.xhtmlDoctype).

Output of CSS styled content is now accessible by default (mailforms, menus, sitemaps, Images, Text with Images, etc.).

Images have accessibility features. You can set an alt and a title attribute for  every image. (integration of extension "cron_cssstyledimgtext")

The "table" content element has now limited accessibility support (integration of extension "accessible_tables")

...more info