function getHttpRequest()
{
var xmlHttp = null;
try
  {  
  xmlHttp=new XMLHttpRequest(); // Firefox, Opera 8.0+, Safari
  }
catch (e)
  {  
  try
    {
    xmlHttp=new ActiveXObject("Msxml2.XMLHTTP"); // Internet Explorer
    }
  catch (e)
    {
    xmlHttp=new ActiveXObject("Microsoft.XMLHTTP");
    }
  }
return xmlHttp;
}