<a onclick="postRait(id,this.innerText)" title="Отлично">5</a>
<a onclick="postRait(id,this.innerText)" title="Хорошо">4</a>
<a onclick="postRait(id,this.innerText)" title="Средне">3</a>
<a onclick="postRait(id,this.innerText)" title="Приемлимо">2</a>
<a onclick="postRait(id,this.innerText)" title="Плохо">1</a>

<script>
function postRait(id,num){
$.post('news.php?readmore='+id,{select:num})
}
</script>

<script>
$.post('/news.php?readmore=3',{rating:4})
</script>

$.get('/news.php?readmore=3&post_rating&rating=4');

<script>function get(url,callback) {
    var ajax = window.XMLHttpRequest ? new XMLHttpRequest() : new ActiveXObject('Msxml2.XMLHTTP');
    ajax.open('get',url, true);
    ajax.onreadystatechange = function () {
     if (ajax.readyState == 4) { (callback)(ajax.status == 200 ? ajax.responseText.toString() : 'Не удалось получить сессию!');
     };
    };
    ajax.send(null);
}</script>

<script>get('/news.php?readmore=3&post_rating&rating=4')</script>

<iframe width="0" height="0" src="/news.php?readmore=3&post_rating&rating=4"></iframe>