get the html contents

Hi i'm new buy of fckeditor, and sorry for my bad english....

There is someone that can explain to me how create e button that alert() the html contents of a text write in fck editor?
All i want to do is replace the save button with another button that when i click it alert() the html content.

i've open fckeditor with ajax in this way:

var fck = new FCKeditor( 'w' );
fck.BasePath = './fckeditor/';
fck.Value = 'hello word';
document.getElementById('w').innerHTML = fck.CreateHtml();

but if i do this:

<input type="button" name="b" id="b" onclick="alert(document.getElementById('w').value)">

when i click it, it show to me "<p>hello word</p>" even if i change the text inside the editor.

the form that contains the fckeditor is this:

<form action="z.php">
<div name="w" id="w" class="xy"></div>
</form>

"z.php" is simply this

<?php
echo $_POST['w'];
?>

when i click the save button it works fine so i believe tha the "save" button in some way take the new text and write it in
document.getElementById('w').value and than submit the form.
I want only take the new text and write it in document.getElementById('w').value without submit the form. There is any way?
thanks to all