How to Use Firebug Add-on in Firefox?

How do you use Firebug add-on in Firefox web browser?

Using Firebug

Firebug is an open source free browser extension available for Mozilla Firefox. Firebug allows live debugging, editing and monitoring websites CSS, HTML, JavaScript, DOM and XHR.
How To Use Firebug In Firefox

In addition to debugging web pages, Firebug is a useful tool for web security testing and web page performance analysis. Firebug makes changes immediately and gives constant feedback to the user. All editors in Firebug support autocomplete. This is a short tutorial that explains you on how to install and uninstall firebug extension in Firefox web browser and the options available in Firebug.