Details: In Firefox 37.0.2, I have 5 pinned tabs plus other regular tabs open. Gmail is logged in and open in a pinned tab. I close FF. Open FF. The pinned Gmail tab on the furthest to the left is now on a sign-in screen. In Gmail, I left click the "Sign in" link (to the left of the blue "Create an account" button) and a regular tab opens. For me, normally center click opens a webpage in a new tab, not left click. Left click normally opens a page in the same tab. In the "One account. All of Google" page, I sign into Gmail and have to repin the tab and move it where I want it. I do not have any Google "accounts" set up, nor is "Stay signed in" check marked. If that is check marked, I get the stupid Google account runaround, which I don't want. Then I have to unpin the pinned Gmail tab that's not logged in. I didn't always work like this. For about a few months, whenever I restarted Firefox, the Gmail pinned tab was already logged in. I don't want to have to always log back into Gmail and pin the tab each time. I do not have 2-step verification in Gmail. In Chrome, this isn't a problem. FF is using Tab Mix Plus options. Will somebody tell me how to fix it?