function validate_email(field,alerttxt)
{
with (field)
  {
  if (value==null||value=="")
    {
    alert(alerttxt);return false;
    }
  else
    {
    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 (validate_email(email,"Please enter a valid email address")==false)
    {email.focus();return false;}
  }
}