using the default leaves the action blank.
the default action of a form tag is to use GET
this is a throw back to earlier version of HTML that did not have a method attribute. for example in HTML 2 to use the POST method you would add it to the action:
<FORM NAME="form1" ACTION="POST http://mydomain.com/page.html">
If you just added the page address to the action:
<FORM NAME="form1" ACTION="http://mydomain.com/page.html">
it would use the GET method.
I believe it was HTML 3 that introduced the method attribute for the form.