If you use Google Docs, you likely appreciate having the right-click menu be the one for Google Docs, and not the one for the browser. If you double-right click, the browser one comes up, so that's there if you need it.
However.
The recent update to Firefox changed things (temporarily) so that all right-clicks brought up the browser menu, not whatever menu the current website was set to bring up.
To correct this and put it back the way it was, go to tools, options, content, and click on the "Advanced" button next to "Enable Javascript"
You need to put a check in the box under "Allow scripts to:" labeled "Disable or replace context menus"
I think it was likely a security change, but it made using Google Docs quite frustrating...