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;
}