$(function() {
// OPACITY OF BUTTON SET TO 75%
$(".fade_in_out").css("opacity","0.85");

// ON MOUSE OVER
$(".fade_in_out").hover(function () {

// SET OPACITY TO 100%
$(this).stop().animate({
opacity: 1.0
}, "fast");
},

// ON MOUSE OUT
function () {

// SET OPACITY BACK TO 50%
$(this).stop().animate({
opacity: 0.85
}, "fast");
});
});