XML http object cross browser

I believe this will be useful for everyone who wants to implement AJAX manually and make it compatible cross browser.

           // cross-browser method to retrieve an XMLHttp object for asynchronous requests & responses
            function GetHTTPRequest()
            {
                var http_request = false;

                if (window.XMLHttpRequest)
                {
                    // Mozilla, Safari,...
                    http_request = new XMLHttpRequest();

                    if (http_request.overrideMimeType)
                    {
                        http_request.overrideMimeType("text/xml");
                    }
                }
                else if (window.ActiveXObject)
                {
                    // IE
                    try
                    {
                        http_request = new ActiveXObject("Msxml2.XMLHTTP");
                    }
                    catch (e)
                    {
                        try
                        {
                            http_request = new ActiveXObject("Microsoft.XMLHTTP");
                        }
                        catch (e) {}
                    }
                }

                return http_request;
            }