Duplicate Tab is a Firefox extension, open a copy of the selected tab, similar to Duplicate Slide Command in Power Point.
Control + Shift +'d would open a new tab with the same content as the selected tab.
You can select this option either from File Menu, or from Content Area Context Menu or from Tab Context Menu.

Requirements:
* Firefox

The license of this software is Freeware, you can free download and free use this browser plug-ins software.