I'm relatively new to Javascript, I've worked in Actionscript 3.0 so I kinda have the hang of syntax, but I'm having an issue with my code working in firefox.

Code:
function loadXML()
{    
	var article = "clientInformation.xml"
	// Load XML from a file on the web server
	if (window.ActiveXObject)
	{
		xmlDoc = new ActiveXObject('Microsoft.XMLDOM');
		xmlDoc.async="false";
		while (xmlDoc.readyState != 4) {} // readyState will be set to 4 when the document is loaded
		xmlDoc.load(article);
		displayXML();
	}
	else if (document.implementation && document.implementation.createDocument) // Broken
	{
		xmlDoc = document.implementation.createDocument("","",null);
		xmlDoc.async="false";
		xmlDoc.onload = displayXML();
		xmlDoc.load(article);
		alert("Is this happening?");
	}
	
} 

//on first load
function displayXML()
{
	document.getElementById("writeup_container").innerHTML = xmlDoc.getElementsByTagName("company").item(0).text;
	
	imageURL = xmlDoc.getElementsByTagName("company")[0].attributes.getNamedItem("image").text;
 	document.getElementById("image_container").innerHTML = "<img src=\"images/ClientSites/" + imageURL + "\"/>"
}
So I have an XML file with information that I want displaying in specific DIVs but when I run it in Firefox The Alert isn't even appearing at one point I had another else alerting if the page couldn't support the script but it wasn't appearing in firefox either.

The Error I'm getting was:
Error: xmlDoc.getElementsByTagName("company").item(0) is null
Line: 34
Code:
document.getElementById("writeup_container").innerHTML = xmlDoc.getElementsByTagName("company").item(0).text;
So there's my problem, any help would be apprecieated, I'm not a hardcore coder so any code please explain what it does <3