Did you also check browser.urlbar.maxRichResults in case you do not get the drop-down list?

Thank you for replying.

I can get drop-down list. Drop-down lsit shows bookmarks and google search results.

but no history items shows. and no auto complete

Does the history work otherwise if you check this in the sidebar or in the History Manager (Library)?

Start Firefox in Safe Mode to check if one of the extensions ("3-bar" menu button or Tools -> Add-ons -> Extensions) or if hardware acceleration is causing the problem.

• switch to the DEFAULT theme: "3-bar" menu button or Tools -> Add-ons -> Appearance
• do NOT click the "Refresh Firefox" button on the Safe Mode start window

• https://support.mozilla.org/en-US/kb/troubleshoot-firefox-issues-using-safe-mode
• https://support.mozilla.org/en-US/kb/troubleshoot-extensions-themes-to-fix-problems

You can check for problems with preferences.

Delete possible user.js and numbered prefs-##.js files and rename/remove the prefs.js file to reset all prefs to the default value including prefs set via user.js and prefs that are no longer supported in current Firefox releases.

• http://kb.mozillazine.org/preferences_not_saved
• http://kb.mozillazine.org/Resetting_preferences

Thank you!!

I found that there is no item in History Manager. So I turned on "Remember my browsing and download history" in the setting -> privacy.

And AutoComplete works normally.