Does anybody else this? I usually use Firefox and usually leave this add on turned on, but I turn it off for sites like Skritter so that I can read the sentences as Skritter intended. However, in the current version of Firefox the little toggle in the lower right hand corner of the screen for the Mandarin popup is missing, so I don't know how to turn the popup on and off any more, short of enabling or disabling and restarting Firefox.

I use Firefox for Mac and an add-on called Perapera something. I click on Tools in the menu bar and in the drop-down menu there's a Perapera item I can click on to activate it.
Is that what you mean?

Zeppa, thanks, but no, I'm not using the Perepra add-in. The one I use is simply called "Mandarin popup." It still works, but I can't turn it on and off from within the screen as I could before. Now I would have to turn it on or off in the drop down menu as you describe and then re-start Firefox. As a workaround I am now using Chrome with a similar popup dictionary called "Zhongwen Poppup Chinese Dictionary" but I would still like to know how to fix the Firefox version since that's my preferred browser.