Show or Hide any firefox tab is very easy with this small firefox addon called HideTab.

Publisher Description

HideTab is a simple Firefox extension to hide/unhide individual tabs.

Install HideTab from here

To hide a Tab you have two methods.

1. Right click the tab you want to hide and click “Hide Tab”.

2.

Click the HideTab icon from the Firefox status bar.
You can see all of your tab titles has been listed in the popup menu.
Simply select the tab you want to hide. That’s it!

To restore a hidden tab, again click on HideTab status bar icon

In the popup menu, You can see the hidden tabs marked with a red icon which is having an exclamation  mark.  Just click on them will bring back your hidden tabs.