Undeclared namespace prefix error (xsl:sort)

Hi there,

I have the following JS partial code to dynamically change the @select attribute
of the XSL file to sort the table.

var xslStr = new ActiveXObject("Msxml2.DOMDocument.4.0");
xslStr.async = false
xslStr.load("note_new.xsl");

var theNode = xslStr.selectSingleNode("//xsl:sort");
theNode.nodeValue = "firstname";

My xsl file look like this:
<content sortcolumn="lastname" sortorder="ascending">
<tr>
<firstname>asdad</firstname>
<lastname>sdlfwle</lastname>
</tr>
<tr>
<firstname>asfasd</firstname>
<lastname>dfpwerwer</lastname>
</tr>
<tr>
<firstname>svowijer</firstname>
<lastname>skwernwler</lastname>
</tr>

<content>

As I test run the code to try to change the node value, I receive an error
with message like:

"Reference to undeclared namespace prefix: xsl"

Does anyone knows how to fix this?

Thanks!

AC