Firefox version 4 has just been released today and all DevExpress ASP.NET products have been tested and verified to work with it!

The enhancements in features and performance are impressive:
Firefox 4 is the fastest Firefox yet. With dramatic speed and performance advancements across the board, Firefox is between two and six times faster than previous releases. Major enhancements to the JavaScript engine make everything from startup time to page load speed to graphics and JavaScript performance screaming fast in Firefox. - Mozilla Blog
v2010 Volume 2.6
Firefox 4 has been in beta for a while and the DevExpress ASP.NET team has been quick to respond to your feedback by fixing reported issues.
So use DXperience v2010 volume 2.6 release or higher when you deploy a website that maybe used in Firefox 4.
Report Issues
If you find a bug with our products in Firefox 4 then please let us know by reporting to the support center.
IE9, Chrome and Safari Supported Too
All DevExpress ASP.NET controls support XHTML, so they have the advantage of being cross-browser compatible! Therefore, our ASP.NET controls work in all major browsers including the outdated Internet Explorer 6.
The new Microsoft IE9 browser is also supported!

Download Firefox 4 and enjoy a faster and safer web experience using DevExpress ASP.NET controls with it!
Build Your Best - Without Limits or Compromise
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Read the latest news about DevExpress ASP.NET MVC Extensions
Download a free and fully-functional version of DXperience now: http://www.devexpress.com/Downloads/NET/

Free DevExpress Products – Get Your Copy Today
The following free DevExpress product offers remain available. Should you have any questions about the free offers below, please submit a ticket via the
DevExpress Support Center at your convenience. We’ll be happy to follow-up.