I have disabled the warning with "do not ask again" check box, now I want to get the warning again. How can I re-enable it?
Open the page about:config in a new tab, and reset the pref
The "Don't ask me again" checkbox only applies to the currently running script.
If you haven't ticked it, the warning will pop up approximately every
dom.max_script_run_time seconds while the script is still running.
Simply refresh the page (or run another script) and you should get the warning again if your script is taking too long.
Go to the
In my Firefox there are now three script variables that are probably changed when checking the checkbox:
dom.max_child_script_run_time dom.max_chrome_script_run_time dom.max_script_run_time
script_run in the search box and it shows just these three. Right-click each one of them that's bold and choose 'Reset'.