var xmlHttp
function GetXmlHttpObject()
{ 
  var objXMLHttp=null
  
  try 
  {
    objXMLHttp = new ActiveXObject("Msxml2.XMLHTTP"); //later IE
  } 
  
  catch (e) 
  {
		try 
		{
    	objXMLHttp = new ActiveXObject("Microsoft.XMLHTTP"); //earlier IE
  		} 
		catch (e) 
		{
		objXMLHttp = null;
  		}
  }
  
  if (objXMLHttp==null)
  {
		objXMLHttp=new XMLHttpRequest() //IE7, Firefox, Safari
  }
  return objXMLHttp
}