You must add a Log In User server behavior to the login page to ensure that the user name and password that a user enters are valid.
When a user clicks the Submit button on the login page, the Log In User server behavior compares the values entered by the user against the values for registered users. If the values match, the server behavior opens one page (usually the site’s Welcome screen). If the values do not match, the server behavior opens another page (usually a page alerting the user that the login attempt failed).