var xmlHttp;

function getXmlHttp()
{

var xmlHttp = null;
try
{
xmlHttp = new XMLHttpRequest();

}
catch(e)
{
try
{
xmlHttp = new ActiveXObject("Msxml2.XMLHTTP");

}
catch(e)
{
xmlHttp = new ActiveXObject("Microsoft.XMLHTTP");

}

}
return xmlHttp;

}