I'm new to ajax, and i try to make a simpe test but i alwas got the system error -1072896748 when i'm calling a page use sing the GET method like : http.open('GET', 'script.php?action=test');
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html xmlns="http://www.w3.org/1999/xhtml">
<meta http-equiv="Content-Type" content="text/html; charset=iso-8859-1" />
<title>Document sans nom</title>
function createRequestObject(){
	var request_o; //declare the variable to hold the object.
	var browser = navigator.appName; //find the browser name
	if(browser == "Microsoft Internet Explorer"){
		/* Create the object using MSIE's method */
		request_o = new ActiveXObject("Microsoft.XMLHTTP");
		/* Create the object using other browser's method */
		request_o = new XMLHttpRequest();
	return request_o; //return the object

/* You can get more specific with version information by using 
	Which will extract an integer value containing the version 
	of the browser being used.
/* The variable http will hold our new XMLHttpRequest object. */
var http = createRequestObject(); 

/* Function called to get the product categories list */
function test(){
	/* Create the request. The first argument to the open function is the method (POST/GET),
		and the second argument is the url... 
		document contains references to all items on the page
		We can reference document.form_category_select.select_category_select and we will 		
		be referencing the dropdown list. The selectedIndex property will give us the 
		index of the selected item. 
	http.open('GET', 'script.php?action=test');
	/* Define a function to call once a response has been received. This will be our
		handleProductCategories function that we define below. */
	http.onreadystatechange = handle; 
	/* Send the data. We use something other than null when we are sending using the POST
		method. */

/* Function called to handle the list that was returned from the internal_request.php file.. */
function handle(){
	/* Make sure that the transaction has finished. The XMLHttpRequest object 
		has a property called readyState with several states:
		0: Uninitialized
		1: Loading
		2: Loaded
		3: Interactive
		4: Finished */
	if(http.readyState == 4){ //Finished loading the response
		/* We have got the response from the server-side script,
			let's see just what it was. using the responseText property of 
			the XMLHttpRequest object. */
		var response = http.responseText;
		/* And now we want to change the product_categories <div> content.
			we do this using an ability to get/change the content of a page element 
			that we can find: innerHTML. */
		//document.getElementById('product_cage').innerHTML = response;

<a href="#" onclick="test()">[test]</a>
<div id="main"></div>
switch($_REQUEST['action']) {
	case 'test':
		echo "main\ntest effectué";