function isChecked(form, element)
{
  with (form)
  {
    for (n = 0; n < elements[element].length; n++)
      if (elements[element][n].checked)
        return true;
    return false;
  }
}


function isEmpty (form)
{
  with (form)
  {
    for (n = 0; n < length; n++)
    {
      if ((elements[n].type == 'text' || elements[n].type == 'textarea' || elements[n].type == 'password' || elements[n].type == 'file') && elements[n].value == '')
      {
        return true;
      }
    }
    return false;
  }
}

function isUsername (username)
{
  if (!username.match (/^\w{1,25}$/))          // \w - [A-Za-z0-9_]
  {
    return false;
  }
  return true;
}


function isPassword (password)
{
  if (!password.match (/^\w{1,15}$/))
  {
    return false;
  }
  return true;
}


function isEmail (email)
{
  if (!email.match (/^[_a-z0-9-]+(\.[_a-z0-9-]+)*@([a-z0-9](-?[a-z0-9])*\.)+[a-z]{2,3}$/))
  {
    return false;
  }
  return true;
}