$(function() {
 // OPACITY OF BUTTON SET TO 100%
 $(".roll").css("opacity","1.0");   
// ON MOUSE OVER 
$(".roll").hover(function () {  
 // SET OPACITY TO 50% 
$(this).stop().animate({ 
opacity: 0.5 
}, "slow"); 
},   

// ON MOUSE OUT 
function () { 
  
// SET OPACITY BACK TO 100% 
$(this).stop().animate({ 
opacity: 1.0
 }, "slow"); 
}); 
});