function validate_email(field,alerttxt)
{
  with (field)
  {
    apos=value.indexOf("@");
    dotpos=value.lastIndexOf(".");
    if (apos<1||dotpos-apos<2) 
    {
      alert(alerttxt);
      return false;
    }
    else 
    {
      return true;
    }
  }
}

function validate_form(thisform)
{
  with (thisform)
  {
    if (ilovebooks.checked == false)
    {
      alert("Don\'t you love books?");
      return false;
    }
    else if (name.value == "")
    {
      alert("Please enter your name.");
      return false;
    }
    else if (validate_email(email,"Not a valid e-mail address!") == false)
    {
      email.focus();
      return false;
    }
    else if (message.value == "")
    {
      alert("Please enter a message.");
      return false;
    }
    else
    {
      return true;
    }
  }
}