.slider{
    opacity: 0;
    display:  block;
    cursor: default;
    position: absolute;
    top: 50%;
    margin-top: -14px;
    height: 27px;
    width: 40px;
    background: url('/arquivos/sprite.png') no-repeat 0 0;
    z-index: 2;
    -webkit-transition: opacity 0.2s linear;
    -moz-transition: opacity 0.2s linear;
    -ms-transition: opacity 0.2s linear;
    -o-transition: opacity 0.2s linear;
    transition: opacity 0.2s linear;
}
.sliderprev{
    background-position: 0px -332px;
}
.slidernext{
    background-position: 0px -332px;
}
.slider.show{
    opacity: 0.8;
}
.slider:hover{
    opacity: 1;
}