var xhr = null; 
function getXhr()
{
	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 ne supporte pas les objets XMLHTTPRequest..."); 
	  xhr = false; 
	  } 
}

function ShowPage(page,a,alt)
{

	getXhr();
	xhr.onreadystatechange = function()
		{
			if(xhr.readyState == 4 && xhr.status == 200)
			{
				document.getElementById('page').innerHTML=xhr.responseText;
			}
		}
	xhr.open("GET","ajax.php?page="+page+"&alt="+alt,true);
	xhr.send(null);
}