function getXhr(){
	var xhr = null;
	if(window.XMLHttpRequest){	
		// FIREFOX
		xhr = new XMLHttpRequest();
	}
	else if(window.ActiveXObject){	
		// IE
		try {
                xhr = new ActiveXObject("Msxml2.XMLHTTP");
            } catch (e) {
                xhr = new ActiveXObject("Microsoft.XMLHTTP");
            }
	}
	else{
		alert("Votre navigateur ne supporte pas les objets XMLHTTPRequest..."); 
		xhr = false;
	}
	return xhr;
}