gistfile1.html

<div id="hidden_form_container" style="display:none;"></div>

gistfile2.js

function postRefreshPage () {
  var theForm, newInput1, newInput2;
  // Start by creating a <form>
  theForm = document.createElement('form');
  theForm.action = 'somepage.php';
  theForm.method = 'post';
  // Next create the <input>s in the form and give them names and values
  newInput1 = document.createElement('input');
  newInput1.type = 'hidden';
  newInput1.name = 'input_1';
  newInput1.value = 'value 1';
  newInput2 = document.createElement('input');
  newInput2.type = 'hidden';
  newInput2.name = 'input_2';
  newInput2.value = 'value 2';
  // Now put everything together...
  theForm.appendChild(newInput1);
  theForm.appendChild(newInput2);
  // ...and it to the DOM...
  document.getElementById('hidden_form_container').appendChild(theForm);
  // ...and submit it
  theForm.submit();
}

gistfile3.html

<!--This is equivalent to submitting this HTML form:-->
<form action="somepage.php" method="post">
  <input type="hidden" name="input_1" value="value 1" />
  <input type="hidden" name="input_2" value="value 2" />
</form>