code :
<li>
<a href="#" id="CustomDecor">
<ul id="sub_menu">
<li><a href="#" id="Carpets"></a></li>
<li><a href="#" id="Storage_Solutions"></a></li>
<li><a href="#" id="Flooring"></a></li>
<li><a href="#" id="Interior_Painting"></a></li>
<li><a href="#" id="Kitchen_Cabinet_Refacing"></a></li>
<li><a href="#" id="Shutters"></a></li>
<li><a href="#" id="Window_Treatments"></a></li>
<li><a href="#" id="Window_Blinds"></a></li>
</ul>
</a>
</li>
Developer tools :

Why am I seeing extra elements? (under sub_menu and first li of sub_menu
You cannot nest anchor (
<a>) elements.On encounter of a new anchor tag, the browser attempts to fix the structure, possibly by closing the previous tag.
Have a look at this simplified fiddle: http://jsfiddle.net/jZr3Z/