Pretty much not, because your profile isn't touched. However, if you want to be sure, you can back up the profile; instructions are given here: http://mzl.la/LHJo6V

Before you install the beta version, back up your profile. You can also back up the bookmarks in a directory outside of the profile. You can find the profile from Help > Troubleshooting Information. If you go back to the grandparent directory of that one, you can back up a folder with the name "Firefox" on it, which helps in identifying it. A new Firefox version is not going to wipe out the profile, but it may modify it so that it is more tricky to go back if you ever want to do that.

Do not use any option to remove personal information, whether from a Firefox or a Windows prompt. You do not even need to uninstall the existing Firefox version.

As long as you follow the suggestions above you will be ok. Firefox will install the Beta over the existing Release without removing your bookmarks.

Additionally it is good practice to occasionally backup your bookmarks manually.

• see Restore bookmarks from backup or move them to another computer

So as a belts and braces procedure why not back them up first.

It is possible to install and run multiple versions of Firefox. Although easy that is often considered advanced or is unnecessary.

thanks guys that was helpful

• http://kb.mozillazine.org/Creating_a_new_Firefox_profile_on_Windows
• http://kb.mozillazine.org/Shortcut_to_a_specific_profile
• http://kb.mozillazine.org/Using_multiple_profiles_-_Firefox
• http://kb.mozillazine.org/Bypassing_the_Profile_Manager

Use the -no-remote command line switch to open another Firefox instance with its own profile and to run different Firefox instances simultaneously, but do not use this with the default browser and the default profile.

• http://kb.mozillazine.org/Opening_a_new_instance_of_Firefox_with_another_profile