I was updating firefox other day and after the update i have found the tabs gone back to default location. I like tabs after web address bar. So, here is how it can be changed if you need.

  1. On your firefox browser write about:config and press enter.
  2. You will be shown a alert message. Click “I will be careful, Promise!”.
  3. write browser.tabs.onTop on search bar.
  4. You should be seen filtered settings. There should be only one. Double click it. and you are done. Close the browser.

Let me know if its worked for you.