If you want to do an ajax call with XMLHttpRequest() there is a pre html5 method and post html5 method. pre HTML5 does not support the onload event for XMLHttpRequest().
var xhr = new XMLHttpRequest();
xhr.open('Get', '/table1.php', true);
/* html5 */
xhr.onload = function(e) {/* script to process data here: data = xhr.response */
mydiv.innerHTML = xhr.response;
}
xhr.send();
Because of differences jquery ajax is much easier.
Pre HTML5 tutorial on XMLHttpRequest http://www.cristiandarie.ro/asp-ajax/Async.html
You can not use AJAX to process an HTML page from a different domain.