Why does the removal of "+-" cause the whole function to not work ?
<p>Code is as shown below.</p>

<pre><code>$('p:first').toggle(function() {
$(this).animate({'height':'+=150px'}, 2000, 'linear');
}, function() {
$(this).animate({'height':'-=150px'}, 2000, 'swing');
});
</code></pre>
