How to keep the browser from saving passwords from my web site

 You know how browsers often say "Do you want Firefox (or whatever) to remember your username and password from this site?" when you fill a username/password form, i want to keep ot from happening in my asp web page. Can anyone help?
 
I know it can be done, the web page of my Bank has a username/password login box and my browser has never asked me that question, and i know the page is on aspx.

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