Mozilla has rolled out Firefox 40, this version focuses on Windows 10 and has a streamlined design. In a blog post, Mozilla explains the new release has bigger, bolder design elements as well as more space for viewing the web. At first sight it doesn't seem to look much different than Firefox 39 though.
Firefox also helps you preserve your choice when using the search field on the Windows 10 taskbar to search the Web. When using this search field, Windows 10 launches your default browser but only shows search results in Microsoft Bing. When you have Firefox set as your default browser on Windows 10, all your Web searches from the taskbar search field will show results in the default search engine you choose in Firefox.
The web browser maker also announced a process to certify Firefox add-ons. In future releases of Firefox, third-party add-ons that have not been certified will be disabled by default to make Firefox safer. In the current version of Firefox this is limited to a warning that you're using unsigned add-ons but so far they aren't automatically disabled.