Menu control generated js causes Sys undefined exception in Web Forms
<p>I'm developing an ASP.NET 4 web application. When I put a Menu control into the web form, the menu causes the following code to generate just before the closing <code>&lt;/form&gt;</code> tag:</p>

<pre><code> &lt;script type='text/javascript'&gt;
         new Sys.WebForms.Menu({ element: 'NavigationMenu', disappearAfter: 500, 
                orientation: 'horizontal', tabIndex: 0, disabled: false });
</code></pre>

<p>As long as I don't use URL Rewriting, the page compiles and loads properly. When I try to use URL Rewriting on the website, Visual Studio starts to throw "Sys is undefined" JavaScript exception.</p>

<p>However, this does not happen always. Most frequently it happens when I change somenting positioning-related in the CSS file, but sometimes the exceptions seems just arbitrary.</p>

<p>How can this be fixed?</p>
