Most browsers have a private browsing or incognito mode to allow you to avoid clearing your browser cache but still start with a clean browsing history. Private or incognito mode can help to diagnose technical issues by bypassing any stored credentials or pages. 

In Firefox, incognito mode is called a private window. To open a private window or tab in Firefox:

1. Click on the Firefox Menu in the upper-right-hand corner of the browser.
2. Select New Private Window.