Remember My password option

I have a login form on which i have 3 Asp.net controls one is txtUserNAme ,txtPassword and btnLogin.

one is for entering username ,other is for password and button for submiting these values .

Now I want to know that how should i give a checkbox having  Remember My password facility so that on next login password automatically fills on entering username .What is the code for that

Plz Help Me!!
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