I have seen different Password masking characters in different logon screens instead of \"a big black dot\". How can I change the Password masking character in password field.
The character displayed depends on the browser, which can choose to print an asterisk, a circle or little pictures of kittens. It's not something the user can control, not to mention the webmaster. The different chars you've seen have probably been in different browsers and/or computers.
However, you can always use good old font-face
CSS attribute to alter the way such character is drawn.