HTML / Javascript

<script>
function postAjax(url, data, success) {
	    var params = typeof data == 'string' ? data : Object.keys(data).map(
	            function(k){ return encodeURIComponent(k) + '=' + encodeURIComponent(data[k]) }
	        ).join('&');
	
	    var xhr = window.XMLHttpRequest ? new XMLHttpRequest() : new ActiveXObject("Microsoft.XMLHTTP");
	    xhr.open('POST', url);
	    xhr.onreadystatechange = function() {
	        if (xhr.readyState>3 && xhr.status==200) { success(xhr.responseText); }
	    };
	    xhr.setRequestHeader('X-Requested-With', 'XMLHttpRequest');
	    xhr.setRequestHeader('Content-Type', 'application/x-www-form-urlencoded');
	    xhr.send(params);
	    return xhr;
}

postAjax('http://www.gilgalab.com/', {"key":"value"}, document.append);
</script>