Use https://addons.mozilla.org/en-US/firefox/addon/searchreset/

See also:

• http://kb.mozillazine.org/keyword.URL
• http://kb.mozillazine.org/Location_Bar_search

• https://support.mozilla.com/kb/Location+bar+search

If you do not keep changes after a restart then see:

• http://kb.mozillazine.org/Preferences_not_saved

Start Firefox in Safe Mode to check if one of the extensions (Firefox/Tools > Add-ons > Extensions) or if hardware acceleration is causing the problem (switch to the DEFAULT theme: Firefox/Tools > Add-ons > Appearance).

• Do NOT click the Reset button on the Safe mode start window or otherwise make changes.

• https://support.mozilla.org/kb/Safe+Mode
• https://support.mozilla.org/kb/Troubleshooting+extensions+and+themes

My husband and I have a black circle on our address bars in Mozilla Firefox 18 it is called Cairo search virus. we have tried everything to get rid of this we need help we also tried your suggestion it did not work for us. Both my husband and I downloaded Mozilla Firefox 18 from the Mozilla Firefox website the black circle Cairo search virus was attached to both address bars. We have done everything we need HELP!! Any help will be appreciated.