var fk_currentFocus = 0;

function fk_getFocus(el) {
  fk_currentFocus = el;
}

function fk_loseFocus(elem) {
  fk_currentFocus = 0;
}

function fk_setFocus(el) {
  if (el == 'login') {
    if (fk_currentFocus != $('username') && fk_currentFocus != $('password')) 
      $('username').focus();
  } else {
    $(el).focus();
  }
}