We have a support article on this, but before I give the link, let me ask a question:

What was the last thing Firefox was doing before you started getting this error? For example:

• browsing normally
• updating to the latest version
• performing a Refresh

In the case of a Refresh, you would find a folder on your desktop named Old Firefox Data, and inside, a recently updated, semi-randomly-named folder that contains your old settings data. If you find that, please let us know because copying it to a different location may be an important step in recovering your settings.

Here's the support article I mentioned: How to run Firefox when your profile is missing or inaccessible.

Yes I can see this folder on my comouter ， thanks What will be my next step Thx jscger2000

Let's see what you have in the normal location for Firefox's profile folders. This is in a hidden place as explained in the support article Profiles - Where Firefox stores your bookmarks, passwords and other user data. Please see the section "Finding your profile without opening Firefox" and if it doesn't refer to Finder, expand the "Editing Tools" in the left column and select Mac as your OS.

Once you get into the Profiles folder, you may see any of the following:

(1) No folders (2) Different semi-randomly-named folder (just ignore this one) (3) Same semi-randomly-named folder as you found in Old Firefox Data

In case #1 or case #2, try this:

Copy the semi-randomly-named folder from "Old Firefox Data" on your desktop to the "Profiles" folder.

Then try the steps in the earlier article about using the Profile Manager to connect to the old folder: Tell the profile manager you want to create a new profile, but use the choose folder button to select the folder you just copied into the Profiles folder (not the one on the Desktop: having Firefox work directly with a folder on the desktop can cause many problems later).

In case #3, before making changes, you would want to compare to see whether the files inside the folder are the same, perhaps it is easiest to check the date/time stamps on some files that Firefox updates frequently such as places.sqlite (history and bookmarks).

If they really are the same, you can use the Profile Manager to connect to the existing copy of the folder: Tell the profile manager you want to create a new profile, but use the choose folder button to select the folder already in the Profiles folder.

You need to locate the profiles.ini file or use the Profile Manager to create a new profile.

You can use one of these to make Firefox create a new default profile or reuse an existing profile:

• Delete the profiles.ini file to force Firefox to create a new default profile
• Use the Profile Manager to create a new profile
  If you still have an existing profile then click "Choose Folder" in the PM and select the location of a lost profile and recover this profile.

You should find the profiles.ini file in this hidden location:

• Windows: %AppData%\Mozilla\Firefox\
  C:\Users\<user>\AppData\Roaming\Mozilla\Firefox\
• Linux: ~/.mozilla/firefox/
• Mac: ~/Library/Application Support/Firefox/

• http://kb.mozillazine.org/Profile_Manager
• https://support.mozilla.org/kb/Managing+profiles
• http://kb.mozillazine.org/Profile_folder_-_Firefox