1. Open Firefox
  2. Enter “about:config” in the URL and press Enter
  3. This will invoke a warning message ” as shown below, Click on the “**I’ll be careful, I promise **” button to open the setting page.
  4. Locate the Filter text box and enter** “browser.tabs.insertRelatedAfterCurrent”**
  5. This will show the key and its value below (which will be enabled)
  6. Double Click on the option to Disable it.
  7. Restart Firefox