When element is not on screen anymore?
<p>In my website, there is a floating cloud(element) that scrolls rightwards, and I wanna be able to tell when it's not visible anymore on screen.</p>

<p>How can I do it?</p>

<pre><code>setInterval(function(){
    if(!jQuery('.sa_cloud_l').is(':visible')){
        alert('not visible anymore');
    }else{          
        c1.css('left', '+=21');
    }
},100);
</code></pre>
