Move footer structure to html.tpl.php
I am not too sure what this error would be caused by but I would recommend instead of putting the footer into the html.tpl.php put a wrapper div around the other elements within the page.tpl.php excluding the footer and styling that wrapper with a specific width.

eg.

    &lt;div class="wrapper" width="960"&gt;
      //all content in here
    &lt;/div&gt;
    &lt;div class="footer"&gt;
      //footer here
    &lt;/div&gt;