AJAX not working in Firefox

[jessicanepom]

I have an ASP program that uses AJAX. Everything is working fine but, when I submit all the information, the value that a COMBOBOX get from AJAX isnt passing to the next form in FireFox. If I use IE, everything works fine.

If you guys can please check my code, i would be glad.

This is the show_city.js that im importing in an ASP file.

var xmlHttp

function MandaID(str)
{
	xmlHttp=GetXmlHttpObject()
	if (xmlHttp==null)
	{
	alert ("This browser does not support HTTP Request")
	return
	}

	var url="select_city.asp"
	url=url+"?state_cod="+str
	url=url+"&sid="+Math.random()
	xmlHttp.onreadystatechange=stateChanged
	
	xmlHttp.open("GET",url,true)
	xmlHttp.send(null)

}

function stateChanged()
{
	if (xmlHttp.readyState==4 || xmlHttp.readyState=="complete")
	{
	document.getElementById("show_city").innerHTML=xmlHttp.responseText
	}
}

function GetXmlHttpObject()
{
	var objXMLHttp=null
	
	if (window.XMLHttpRequest)
	{
	objXMLHttp=new XMLHttpRequest()
	}
	else if (window.ActiveXObject)
	{
	objXMLHttp=new ActiveXObject("Microsoft.XMLHTTP")
	}
	return objXMLHttp

}