It highlight "Password second line " compile error. Method o data member not found.
Code:
Private Sub Command10_Click()
    If Me.Password = DLookup("password", "users", "username = '" & Me.UserName & "'") Then
        Me.ID DLookup("id", "users", "username = '" & Me.UserName & "'")
        DoCmd.OpenForm "main"
...