Firefox 4.0.1, an update to your version 4.0, was released about a month ago.

To update Help > About Firefox, click Check for Updates.

See:

• https://support.mozilla.com/en-US/kb/Updating+Firefox?bl=n&s=update%20automatically
• http://kb.mozillazine.org/Software_Update#Software_Update_not_working_properly
• http://support.mozilla.com/en-US/kb/Installing+Firefox+on+Mac

You need to update the following. The Plugin version(s) shown below was/were submitted with your question and is/are out of date. You should update to avoid known security issues with the version(s) you have installed. Click on "More system info..." to the right of your question to see what was included with your question.

• Shockwave Flash 10.2 r152

1. Check your plugin versions on either of the following links':
   • http://www.mozilla.com/en-US/plugincheck/
   • https://www-trunk.stage.mozilla.com/en-US/plugincheck/
   • Note: plugin check page does not have information on all plugin versions
   • There are plugin specific testing links available from this page:
     • http://kb.mozillazine.org/Testing_plugins
2. Update the Flash plugin to the latest version. See: https://support.mozilla.com/en-US/kb/Managing%20the%20Flash%20plugin#w_updating-flash

I did as suggested: updating to Firefox 4.0.1, but when I reopened Firefox, it still automatically downloaded 4.0. Any other suggestions?

1. download and save the installer to your hard drive in a place where you can find it later.
   • download from: https://www.mozilla.com/en-US/firefox/new/
2. Quit Firefox: click on the Firefox menu and select Quit Firefox.
3. Uninstall Firefox
   • Open the Applications folder.
   • Drag the Firefox application to the Trash.
     • IMPORTANT: If given an option to delete your personal data, do NOT do so (i.e., do NOT check the box)
   • Your personal data (passwords, bookmarks, etc.) should be safe as they are stored in a different location
     • For safety sake, you might want to backup your personal data; see: https://support.mozilla.com/en-US/kb/Backing%20up%20your%20information#os=mac&browser=fx4
   • Your uninstall of Firefox is finished.
4. Install the version you downloaded; see: http://support.mozilla.com/en-US/kb/Installing+Firefox+on+Mac

I appreciate your response, but after doing all that was suggested, Firefox 4.0 still downloaded automatically.