getElementsByTagName is not working Simple JS
<p>another quesion: <a href="http://jsfiddle.net/ajinkyax/qGzTY/1/" rel="nofollow">http://jsfiddle.net/ajinkyax/qGzTY/1/</a>
Above link shows a js calculator, but whn u click nothign happens</p>

<p>Im just amazed why this simple function not working!!!.</p>

<p>I even tested with a tag, still it wont wokr. getElementsByTagName("a")</p>

<pre><code>&lt;!DOCTYPE html&gt;
&lt;html lang="en"&gt;
    &lt;head&gt;
        &lt;meta charset="utf-8" /&gt;
        &lt;title&gt;documentElement&lt;/title&gt;
    &lt;/head&gt;
    &lt;body&gt;
         &lt;p&gt;This is 4rth child (3)&lt;/p&gt;
        &lt;p&gt;This is 4rth child (3)&lt;/p&gt;

        &lt;p&gt;This is 5th child (4) &lt;span id="some"&gt;CHANGE THIS&lt;/span&gt;&lt;/p&gt;

        &lt;script type="text/javascript"&gt;
            var mySpan = document.getElementsByTagName('span');

            mySpan.innerHTML = 'This is should change';

        &lt;/script&gt;
    &lt;/body&gt;
&lt;/html&gt;
</code></pre>
