what's wrong with this?

[AFemaleProdigy]

Hey everyone! I unfortunately have to work with someone else's coding on this new project. I get a parse error every time I try to put this into my headinclude. I don't know this type of code. Can anyone tell me what is wrong with it?

Thanks!

<script type="text/javascript">
     $(document).ready(function(){
  $('#mainMenu > li').hover( function() { $(this).addClass('hover') }, function() {$(this).removeClass('hover')});
     });
 </script>