$(document).ready(function(){
$(".imgthumb img").fadeTo("slow", 1.0); // This sets the opacity of the thumbs to fade down to 30% when the page loads
$(".imgthumb img").hover(function(){
$(this).fadeTo("slow", 0.5); // This should set the opacity to 100% on hover
},function(){
$(this).fadeTo("slow", 1.0); // This should set the opacity back to 30% on mouseout
});
});