function validate_email(field,alerttxt) {
  with (field) {
    apos = value.indexOf("@");
    dotpos = value.lastIndexOf(".");
    str = new String(value);
    len = str.length;
    if ((apos>0) && (dotpos > apos+1) && (dotpos < len - 1)) {
      return true;
    }
    
    else {
      alert(alerttxt);
      return false;
    }
  }
}

function validate_form(thisform) {
  with (thisform) {
    if (validate_email(email,"Neplatna emailova adresa!") == false) {
      email.focus();
      return false;
    }
  }
}