The two primary causes of unusual behavior in Mozilla Firefox and Yahoo! Toolbar are:

• A corrupt Firefox profile
• Extension conflicts

Your user profile can become corrupt if the browser crashed or your computer halted unexpectedly. The following steps resolve many common problems associated with Mozilla Firefox.

First, update all your extensions and themes. Due to the large number of extensions that have been written for Mozilla Firefox, it's impossible to test every possible permutation and combination. When extension conflicts occur, extensioin authors release updated versions of their extenstions as these problems are discovered. If you have any Firefox extensions installed, check to make sure you have the most recent versions installed by doing the following:

1. Select "Options" from the "Tools" menu.
2. Select the "Advanced" tab in the Options window.
3. In the "Software Update" section ensure that "My Extensions and Themes" is checked.
4. Click "Check Now" to check for updates for your extensions.
5. Install any updated extensions that are found.
6. Restart your browser.

If you're still seeing problems, your user profile might be corrupt, or you might still have an extension conflict. Start Firefox in "Safe" mode from the "Mozilla Firefox" folder and see if the problem persists. If yes, you need to create a new user profile.

If the problem does not persist, you're most likely suffering from an extension conflict. Uninstall the extension you most recently installed and see if the problem persists. Typically, the problem will disappear and you should report the bug to the extension author.

Please see the Mozilla Firefox FAQ for more information and suggestions for troubleshooting Mozilla Firefox problems.