HTML5 Validator: Bad value "" for attribute "action" on element "form": Must be non-empty

You could just write action="#" instead of leaving it empty. This makes the attribute "action" non-empty so that the error message will no longer be displayed and at the same time, the script still remains independent from the page from which it was called.

This would switch your form to that:

<form action="#" method="post" id="myform">
  <input type="input" name="name">
  <input type="submit" name="submit" value="Send">
</form>

If you only want to have the # within your HTML code, you can also try to remove it with JavaScript after parsing:

document.getElementById("myform").setAttribute("action", ""); 

To ensure that the attribute is removed from the correct form, I have added the ID "myform" to your form, so that we can properly access it.
2016-02-21 at 19:54

You can also use PHP in order to always insert the current page as action-attribute.

For example like that:

<form action="<?php 

echo htmlspecialchars($_SERVER["PHP_SELF"]);

?>" method="post" id="myform">
  <input type="input" name="name">
  <input type="submit" name="submit" value="Send">
</form>

Of course, if it is not necessary to make it dynamic and if you know the recipient page, the easiest way would be to just insert the recipient page behind "action" to get rid of this error.
2016-02-23 at 20:15