PageTitler.html

<html>
<head><title>Blank page</title></head>
<script>
function setTitle(newTitle) {
  document.title = decodeURI(newTitle.replace(/_/g, " "));
}
function setTitleFromForm(e) {
  if (e.preventDefault) { e.preventDefault(); }

  var newTitleElem = document.getElementById("newTitle");
  var newTitle = newTitleElem.value;
  document.title = newTitle;

  var myURL = document.location + "";
  var newURL = myURL.replace(/[?#].*/, "") + "?" + newTitle;
  document.location = newURL;
  return false;
}

window.onload=function() {
  var form = document.getElementById("theForm");
  form.onsubmit = setTitleFromForm;

  var myURL = document.location + "";
  var currTitle = myURL.replace(/.*[?]/, "");
  setTitle(currTitle);

  var input = document.getElementById("newTitle");
  input.value = decodeURI(currTitle);
  input.focus();
}

</script>
<style type="text/css">
  #notes, #newtitle { width: 400px; }
  #notes            { height: 300px; }
</style>
<body>
<form id="theForm" onSubmit="setTitleFromForm" method="get">
  <input type="text" id="newTitle" />
  <button type="submit">Set title</button>
  <br><br>
  <textarea id="notes">
  </textarea>
</form>
</body>
</html>