@media (min-width: 800px) {
.left { display:none; }
.right { display:none; }
}
@media (max-width: 799px) {

.bottom_left { position:fixed; left:0px; bottom:0px; width:50%; height:50px; line-height:50px; font-weight:800 ; color:#fff; background-color:steelblue; text-align:center; z-index:99999; cursor:pointer }
.bottom_right { position:fixed;  right:0px; bottom:0px; width:50%; height:50px; line-height:50px; font-weight:800 ; color:#fff; background-color:royalblue; text-align:center; z-index:99999; cursor:pointer }
}