Not on FF40 Rated 1 out of 5 stars
On FF40 [Windows 7 system] it is inert; doesn't work.
for addon users Rated 5 out of 5 stars
Addon still works on palemoon. For firefox 29 use "Smaller View" addon or "Small Tabs"
about time! Rated 5 out of 5 stars
Very good add on to free up a little more screen space!