NoSquint is a Firefox add-on that allows you to adjust the text-only and full-page zoom levels as well as color settings both globally (for all sites) and per site.
Whenever I change the zoom level on a tab, all other tabs change to match. After investigating, I discovered that the domain for all tabs was "about:blank", regardless of the actual domain. What might be significant is that I have three windows open, one with five open tabs, another with 12, and another with over 50. I also use tab groups to switch the window with the most tabs to other groups at various times.
Mozilla/5.0 (Windows NT 6.1; WOW64; rv:21.0) Gecko/20100101 Firefox/21.0
Whenever I change the zoom level on a tab, all other tabs change to match. After investigating, I discovered that the domain for all tabs was "about:blank", regardless of the actual domain. What might be significant is that I have three windows open, one with five open tabs, another with 12, and another with over 50. I also use tab groups to switch the window with the most tabs to other groups at various times.
Mozilla/5.0 (Windows NT 6.1; WOW64; rv:21.0) Gecko/20100101 Firefox/21.0