How to turn login captcha on off
In order to enable/disable captcha text in admin login form you should:
1. Log in into admin panel
2. Go to "Advanced Content Editing" tab
3. Click "System options"--> "Site configuration" --> "Default set"
4. In dropdown list "Show CAPTCHA at login?" select "Yes" or "No" in order to enable or disable captcha
5. Press "Save element" button