function getXhr() {
		var xhr = null;
		if(window.XMLHttpRequest)
			xhr = new XMLHttpRequest();
		else if (window.ActiveXObject) 
		{
			try
			{
			xhr = new ActiveXObject("Msxml2.XMLHTTP");
			}
			catch(e)
			{
			xhr = new ActiveXObject("Microsoft.XMLHTTP");		
			}
		}
		else
		{
		alert("Votre navigateur n'est pas compatible Ajax");
		xhr=false;
		}
		return xhr;
}