<div id="pa-container"><input type="hidden" /></div> <script type="text/javascript" src="http://www.youpolls-sondaggi.it/components/com_communitypolls/assets/scripts/pollsanywhere.js"></script> <script type="text/javascript">PollsAnywhere({id:13});</script>

This is the code CP give for embed. it doesn't work . I also follow instruction you wirte in

If you use TinyMCE/JCE, it will strip and script tags for security reasons. You can see the below page to know how you can enable it

http://www.joomlablogger.net/joomla-tips/joomla-templates/how-to-easily-add-javascript-snippets-to-joomla/

Thanks
Marco