cd7c41b5_ebug_Preferences___FirebugWiki__Description
[Option] detachedFirebugOnTop [Valid Values] true, false [Default] false [UI Equivalents] Firebug Menu->Options->Detached Firebug on Top [Description] 
Specifies whether the Firebug window shall always be shown above all other windows
Firebug Preferences - FirebugWiki