How do I uninstall the Ask Toolbar or Search App from Mozilla Firefox in Mac OS X?

To uninstall the Ask Search App, click on Firefox's Tools menu and choose Add-ons.

From your Add-ons page, find the Ask search extension in the list of installed extensions, and click "Remove" at the right edge of the extension listing. You may need to restart your browser in order to complete the removal.

After that, you may also wish to change your default homepage in Firefox. To do so, refer to this article.