Cannot add or change bookmarks in Firefox
If you are having the problem of firefox not allowing you to add a bookmark, try the following steps they worked for me. I tried the steps laid out by Mozilla located Here , with little success.
I am using FF Version 51.0, here is what I did.
Locate the users Preferences (HD/Users/UserName/Library/Preferences) folder and open it.
Inside that folder will be .plist files that need to be deleted. Delete any .plist file with mozilla or firefox in the name. These will be recreated when the application opens next.
Open Application support folder (HD/Users/UserName/Library/Application Support). In here will be a folder for Mozilla or Firefox, there may even be a folder for each. Delete the folder(s).
Launch firefox again, go through the initial setup and see all the problems go away.
**Note: This will erase all settings and content in firefox. bookmarks, passwords, history, etc...