appendchild in javascript not workign in mozila

Hi friends,
i need a help.. in javascript part
iam using sarisa to open dom document and write some xml content in it and posting it to anohter page.. the problm is append child is not working . its doesnt givign a error.. but when i display the content it shows undefined.mine is workign fien in Ie but it doesnt work in Mozila

var objXMLDoc = Sarissa.getDomDocument();
objXMLDoc.async =false;

//creates processing instruction element and adds it to the return dom document
objXMLDoc.appendChild(objXMLDoc.createProcessingIn struction("xml", "version='1.0'"));


//builds the document with the Contact details
objXMLNode = objXMLDoc.createElement("root");
objXMLNode.setAttribute("districtID", document.villageForm.cmbDist.value);
alert(objXMLNode.getAttribute("districtID"));
//iam getting the attribute her both in Mozilla and IE
objXMLDoc.appendChild(objXMLNode);
alert(objXMLDoc.xml)
//this alert contains xml content in IE but in mozila it dispalys undefined.. i could not figure out the problm..
only append child not working plz help me i this issue.

Thanks in advance

moved to Javascript forum