How do I set up Firefox to keep only cookies from select sites, when I use Firefox-Sync? I use Firefox on a desktop iMac, a MacBook and my Android Samsung Galaxy S III mobile phone. All installations of Firefox are set to sync over Firfox's inbuilt Firefox-Snyc feature.

On my desktop computer I have set Firefox to delete all cookies when I close Firefox and defined exceptions, telling Firefox to keep cookies from those sites. I followed this instruction.

This worked fine at first: I visited some sites, closed Firefox, opened Firefox, looked at the cookies, and all cookies had been deleted except those from the excepted sites.

But after I began using Firefox on my other computers, I noticed that:

(a) all cookies were being deleted sometimes; sometimes all remained

(b) the exceptions disappeared sometimes; sometimes they remained

So the question is:

How do I set up Firefox to keep only cookies from select sites, when I use Firefox-Sync?
Firefox Sync doesn't support site permissions, unfortunately.

It's been requested with bug 470699: add yourself to the CC list to be notified of future development.