@media (min-width:320px) and (max-width:480px) { /* smartphones, iPhone, portrait 480x320 phones */
    .backtop {
        right: 20px;
    }
}

@media (min-width:481px) and (max-width:640px) { /* portrait e-readers (Nook/Kindle), smaller tablets @ 600 or @ 640 wide. */
    .backtop {
        right: 20px;
    }
}

@media (min-width:641px) and (max-width:960px) { /* portrait tablets, portrait iPad, landscape e-readers, landscape 800x480 or 854x480 phones */
    .backtop {
        right: 20px;
    }
}

@media (min-width:961px) and (max-width:1024px) { /* tablet, landscape iPad, lo-res laptops ands desktops */

}

@media (min-width:1025px) and (max-width:1280px) { /* big landscape tablets, laptops, and desktops */

}

@media (min-width:1281px) { /* hi-res laptops and desktops */

}