getElementById vs. getElementsByTagName
<p>Basic question.</p>

<pre><code>document.getElementById("yy").onmouseover = hi;
//document.getElementsByTagName("li").onmouseover = hi;
...
</code></pre>

<p>In this example, <a href="http://jsfiddle.net/8fURz/1/" rel="nofollow">http://jsfiddle.net/8fURz/1/</a> why does the first line work, but not the second line (when it is un-commented, of course)?</p>

<p>I know I can do this easily with jQuery, just wonderin...</p>
