Make sure you are not entering any leading or trailing spaces. I was able to use a standard test number:
and not get an error.
as for the menu, looks like this script on your page:
<link href="ui_totop/css/ui.totop.css" rel="stylesheet" />
<script src="ui_totop/js/jquery.ui.totop.js" charset="utf-8"></script>
is changing the nav color dynamicly.