jQuery selector using a string as context
<p>From the <a href="http://api.jquery.com/jQuery/#jQuery1" rel="nofollow">jQuery docs</a>, I can see that I should be able to pass a context with a selector to restrict the selector to only matches within that context.</p>

<p>For some string contexts, this works fine:</p>

<pre><code>&gt;&gt;&gt; jQuery('a', '&lt;div&gt;&lt;a id="foo"/&gt;&lt;a id="bar"/&gt;&lt;/div&gt;')
[a#foo, a#bar]
</code></pre>

<p>For others, not so much:</p>

<pre><code>&gt;&gt;&gt; jQuery('a', '&lt;html&gt;&lt;body&gt;&lt;a id="foo"/&gt;&lt;a id="bar"/&gt;&lt;/body&gt;&lt;/html&gt;')
[]
</code></pre>

<p>If I've got a complete HTML document as a string, and I want to use jQuery to pull elements out of it, how should I do that?</p>
