validation for login page with radio button, if click on super admin radio button,i s

Code:
<td><font color="white">Role</font></td>
<td>
 <input type="radio" id="sa" name="admin"><font color="white">Superadmin</font></input>
 <input type="radio" id="ad" name="admin"><font color="white">Admin</font></input>
...