$(document).ready(function(){
$("#cat-box img, .cat-box img").fadeTo("fast", 1.0); // This sets the opacity of the thumbs to fade down to 60% when the page loads

$("#cat-box img, .cat-box img").hover(function(){
$(this).fadeTo("fast", 0.5); // This should set the opacity to 100% on hover
},function(){
$(this).fadeTo("fast", 1.0); // This should set the opacity back to 60% on mouseout
});
});