jQuery show extra field conditional on current input's value
<p>Sorry to ask such a basic question. Say, I have two inputs. The first one is always visible, while the second shows up only when the first one's value is less than 0. I tried to use .change to implement this activity, however it does not work. So can anyone give me some suggestions? 
Thanks in advance.</p>

<p>HTML code:</p>

<pre><code>&lt;table&gt;
&lt;tr&gt;&lt;th&gt;&lt;label for="id_first"&gt;First input:&lt;/label&gt;&lt;/th&gt;&lt;td&gt;&lt;input type="text" name="First input" id="id_first" /&gt;&lt;/td&gt;&lt;/tr&gt;
&lt;tr&gt;&lt;th&gt;&lt;label for="id_second"&gt;Second input:&lt;/label&gt;&lt;/th&gt;&lt;td&gt;&lt;input type="text" name="First input" id="id_second" /&gt;
&lt;/td&gt;
&lt;/tr&gt;
&lt;/table&gt;
</code></pre>

<p>jQuery code</p>

<pre><code>&lt;script type="text/javascript" src=" ../stylesheets/jQuery-1.7.2.js"&gt;&lt;/script&gt; 

&lt;script&gt;
$(document).ready(function() {
    $('#id_second').closest('tr').hide();
    $('#id_first').change(function() {    
    if ($(this).val() &lt;0){
        $('#id_second').show()}    
    else{
        }
    });​​ 
</code></pre>
