$(function(){
    var d = $('div#category_images img.default');  //define default image to fade back in
    var t = 600;                                   // universal time for animation
   
   $(document).ready(function(){
      d.fadeIn(t);
   });


   $('ul#sub_nav a')
          .mouseover( function() {
             d.fadeOut(t); 
             var slide = $(this).attr('class');
             var img = $('img.'+slide);
        	        if ($('img.active').length) { // implies *not* zero
        	  			 
        	  			 	 $('div#category_images img.active').hide(function(){
        		           		img.addClass('active').fadeIn(t);
        		          	   });	  			 
        				  } else {
        				   img.addClass('active').fadeIn(t);
        				  }
            
        	 })
          .mouseout( function(){
             var slide = $(this).attr('class');
             var img = $('img.'+slide);
             img.removeClass('active').fadeOut(t);
             //d.fadeIn(t);
          });
          	
          
         

	});