var xmlhttp = false;


if (window.XMLHttpRequest){ // Se o browser for Mozilla, Safari etc.
xmlhttp=new XMLHttpRequest();
}
else if (window.ActiveXObject){ //Se for o Internet Explorer
try {
xmlhttp=new ActiveXObject("Microsoft.XMLHTTP");
}
catch (e){}
try{
xmlhttp=new ActiveXObject("Msxml2.XMLHTTP");
}
catch (e){}

}