JQUery validation plugin for checking data availability
<p>I am learning how to use JQuery validation plugin,
I got a simple input text field like this:</p>

<pre><code>&lt;input type="text" name="username"&gt;
</code></pre>

<p>But I don't know how to use this plugin to do some data availability tasks.</p>

<p>Could you help me please?</p>
