Modo Seguro é um modo especial de execução do Firefox que pode ser usado para solucionar problemas no Firefox. No Modo seguro, você pode redefinir algumas configurações ou desativar extensões e temas que possam ser a origem de problemas. Comparando o comportamento do Firefox no modo normal ao seu comportamento no modo de segurança com vários itens desabilitados, você pode ser capaz de diagnosticar problemas.

How to start Firefox in Safe Mode

Safe Mode window

You now have three options:

• Clicking the Exit cancels your attempt to get into Firefox's Safe Mode.
• Clicking the Continue In Safe Mode starts Firefox in its Safe Mode. While you are in Safe Mode, your extensions and themes will be disabled, and any toolbar customizations will be reverted back to their defaults. These changes are not permanent - when you leave Safe Mode and start Firefox up normally, your extensions, themes, and settings will return to the state they were in before you entered Safe Mode.
• The Make Changes and Restart is only enabled if you select one of the boxes above it:
  • Disable all add-ons: If you select this box and then click Make Changes and Restart then Firefox will start back up in its normal mode, except all your extensions and themes (but not plugins) will be disabled. (Not uninstalled.)
  • Reset toolbars and controls: If you select this box and then click Make Changes and Restart then Firefox will start back up in its normal mode, except any toolbar customizations you have made will be lost, such as position of buttons and toolbars,
  • Reset bookmarks to Firefox defaults: If you select this box and then click Make Changes and Restart then Firefox will delete your current bookmarks and replace them with its default set.
  • Reset all user preferences to Firefox defaults: If you select this box and then click Make Changes and Restart then any changes you have made to Firefox's options will be set back to their default settings.
  • Restore default search engines: If you select this box and then click Make Changes and Restart then any of the default search engines you deleted will be restored.

Exiting Safe Mode

1. No topo da janela do Firefox, clique no botão Firefox (menu Arquivo no Windows XP) e então clique em SairNo topo da janela do Firefox, clique no menu Arquivo e selecione SairNa barra de menus, clique no menu Firefox e selecione Fechar o FirefoxNo topo da janela do Firefox, clique no menu Arquivo, e então selecione Sair
2. Start Firefox as you normally would.

• • If Firefox keeps starting in Safe Mode see Firefox só funciona em modo seguro.

__Based on information from Safe mode (mozillaZine KB)}