From Mozilla:

Just four months after the release of Firefox 3.0, Mozilla has announced the availability of Firefox 3.1 beta 1.  With this latest version, Mozilla continues to make it easier for users to quickly take advantage of the power of the Web, and for Web application developers to build engaging experiences.

The main work in beta 1 has been done on Web compatibility as well as enablement of new Web features such as geolocation, video, offline application support and CSS improvements.

New features and changes include:

  • Web standards improvements in the Gecko layout engine
  • Added support for CSS 2.1 and CSS 3 properties
  • A new tab-switching shortcut that shows previews of the tab you're switching to
  • Improved control over the Smart Location Bar using special characters to restrict your search
  • Drag and drop tabs from one Firefox window to another.
  • Support for new web technologies such as the

Please note that while Mozilla invites everyone to help test this beta, they remind users that it's not a fully completed product so there may be some rough edges visually and with the user experience.  A second beta is scheduled for later this year to early next year, and the release of the product will be in early 2009.

For more information, visit the DevNews post here: http://developer.mozilla.org/devnews/

You can download Mozilla Firefox 3.1 Beta 1 here.