More issues with Firefox

I have noticed that the grey-tones button has reappeared in FF and it does work now, except that it causes a couple of issues:

• if you’re logged in, the black administration toolbar on top disappears, although if you hover where it should be you can still access its menus; this happens not only on my website (www.setificio.gov.it) but also on others I know of, and on versions of FF both for Mac and for Windows
• if I use FF on iMac and ONLY on my website, the plugin toolbar disappears when I select the grey-tones and if the browser window is open wide (so there’s no way of toggling back to normal); if I make the window smaller it reappears. It doesn’t happen on FF for Windows.

I have checked on other browsers: everything seems to be ok on Safari for iMac as well as for Chrome for Windows. IE8 for Windows on the other hand toggles to grey most of the website but not the menus on the two sidebars. Strange! (I wouldn’t worry about this though).
The iMac I use is a 21″ one; the Windows laptop is an old 15″ one and runs on XP. WP and the plugin are updated.
Thanks in advance!
Claudia

https://wordpress.org/plugins/wp-accessibility/