Utilu Mozilla Firefox Collection contains multiple versions of the free web browser Mozilla Firefox, which are standalone so they can be used at the same time. This is useful for web developers. In Utilu Mozilla Firefox Collection you can quickly see how your websites look when rendered using different versions of the Gecko render engine. The version number of each included version of Mozilla Firefox can be found in the window title. Utilu Mozilla Firefox Collection also includes the Firebug and Web Developer add-ons for all included versions of Mozilla Firefox. These add-ons provide a variety of tools which make troubleshooting websites much easier.