Javascript getElementByID().innerHTML() not working
<p>I'm new to Javascript and for some reason I can't get the following code to work and it's driving me crazy!</p>

<p>It's</p>

<pre><code>    &lt;!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd"&gt;
&lt;html xmlns="http://www.w3.org/1999/xhtml" xml:lang="en" lang="en"&gt;
&lt;head&gt;
    &lt;title&gt;title&lt;/title&gt;
    &lt;meta http-equiv="Content-Type" content="text/html; charset=utf-8" /&gt;
    &lt;meta name="description" content="test" /&gt;
    &lt;meta name="keywords" content="test" /&gt;
    &lt;meta name="robots" content="index,follow" /&gt;
&lt;/head&gt;

&lt;body&gt;
    &lt;h1&gt;test&lt;/h1&gt;
&lt;p id="demo"&gt;something&lt;/p&gt;

&lt;button type="button" onclick="myFunction();"&gt;Try it&lt;/button&gt;

&lt;script type="text/javascript"&gt;
        function myFunction() {
            document.getElementByID("demo").innerHTML = "testttt";
        }
    &lt;/script&gt;


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

<p>Anyone know the problem?</p>
