SetTimeout don't work correctly
<p>I think the pop window with OK string will be dislayed afetr 5s after I click the button, but the pop window dispalyed  immediately after I click the button, why?</p>

<p>Thanks!</p>

<pre><code>&lt;html&gt;
&lt;head&gt;
    &lt;title&gt;Wake up call&lt;/title&gt;
    &lt;script type="text/javascript"&gt;
        function wakeUpCall() { // Function is defined here
            setTimeout(aa("ok"), 5000);
        }

        function aa(bb) {
            alert(bb);
        }
    &lt;/script&gt;
&lt;/head&gt;
&lt;body bgcolor="lightblue"&gt;
    &lt;form&gt;
        &lt;input type="button"
            value="Wake me"
            onclick="wakeUpCall()"&gt;
    &lt;/form&gt;
&lt;/body&gt;
&lt;/html&gt;
</code></pre>
