change img src and width
<p>I change the scr of an img tag using jQuery, such as,</p>

<pre><code>$("#img1").attr("src", "pic1.png");
</code></pre>

<p>after this, I try to get the width of img (it's not set in html),  </p>

<pre><code>$("#img1").width();
</code></pre>

<p>it seems the width is not changed with the src, did I miss something? thanks.</p>
