- Go to "my preferences", and click save button.
- On this new page, you'll get a green message indicating that you've successfully updated your preferences. Now click on the "Special page" tab; you should expect to land on Special:Preferences. Instead, you land on Special:Preferences&success and the green message is shown again.
This causes confusion; by clicking on the special page tab, you're not updating preferences so you shouldn't get the green dialog.