[jQuery] Add an animate function to a addClass?

[123gotoandplay]

Hi all,

why doesn't this work? it doesn't color red
  $.fn.hoverClass = function(c) {
                        return this.each(function(){
                                $(this).hover(
                                        function() { 
$(this).addClass(c).animate({ marginLeft: '+=5px' },
200); },
                                        function() { 
$(this).removeClass(c).animate({ marginLeft: '-
=5px' }, 200); }
                                );
                        });
                };

.navHover {
background-color:#FF0000;
}