function kwdComment(obj){
if (obj.value == obj.defaultValue){
  obj.value = "";
  obj.style.color = "";
}
}

function check_keyword() {
  if (document.search_form.form[mail].value == "メールアドレスを入力"){
    document.search_form.form[mail].value = "";
  }
  document.search_form.submit();
}