The sixth beta release in the new Firefox 24.x branch has been made available for download by Mozilla, for all available platforms, including Linux.The binaries for Mozilla Firefox 24 Beta 4 can be downloaded and run without having to install anything. This is true for all the available platforms.
The previous version of Firefox, 23, had ten Beta versions before reaching the final version. There are no details about this particular Beta release, but a detailed list of upcoming features and other various changes can be found on the official website.
Download Mozilla Firefox 24 Beta 6 for Windows
Download Mozilla Firefox 24 Beta 6 for Linux
Download Mozilla Firefox 24 Beta 6 for Mac OS X
Remember that this is a development version and it should NOT be installed on production machines. It is intended for testing purposes only.