user login form: name and password default values Currently, when the user is loggged out, on user login form, the username field is filled with text, which probably is taken from a cookie (not sure) - it is the name of someone who logged in before. The password is also filled with dots, representing previously logged in password.

How to prevent it, i.e. always display username and password fields empty?

P.S. Why I need this? Because the requirement is that in the user name box there is a placeholder behavior with text "Username". (HTML5 placeholder). I noticed that it works well when the browser has no username remembered and does not work at all when the browser remembers the username and password.
Usually, it's the browser that remembers login names and passwords, allthough some sites place a cookie upon successful login that they use to populate the username field on your next visit.

I don't think Drupal does this by default so I think in your case, it's the browser that remembers the login name and password.

There is one way to avoid this and that's by changing the name of the form fields. Browsers 'know' to remember usernames because the name of those fields is usually something like 'user', 'username' or 'login'.

If you change the name attrribute of the login input field to, say, 'bycicle', browsers will stop remembering those values automatically.