$(document).ready(function(){
$(".col_1 img, .col_2 img").fadeTo("fast", 1.0); // This sets the opacity of the thumbs to fade down to 60% when the page loads

$(".col_1 img, .col_2 img").hover(function(){
$(this).fadeTo("fast", 0.6); // 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
});
});