adding remember me check box

iam planning to have a remember me check box for my login page

i have included

FormsAuthentication.RedirectFromLoginPage(txtUserName.Text, chkRemMe.Checked);

FormsAuthentication.SetAuthCookie(txtUserName.Text + "/" + txtPassword.Text, chkRemMe.Checked);

but it seems to be not happening what shd i do .Please help me with clear steps
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