.adverts_top {
    text-align: center;
}                
.adverts_left {
    position: fixed;
    top: 0;
    left: 0;
    display: none;
    text-align: center;
}             
.adverts_right {
    position: fixed;
    top: 0; 
    right: 0;
    display: none;
    text-align: center;
}
.adverts_billboard {
    text-align: center;
}                
.adverts_rectangle {
    text-align: center;
} 

@media screen and (min-width: 1600px) {
    .adverts_left {
        display: block;
        width: 18%;
    }
    .adverts_right {
        display: block;
        width: 18%;
    }                    
}
@media screen and (min-width: 1800px) {
    .adverts_left {
        display: block;
        width: 22%;
    }
    .adverts_right {
        display: block;
        width: 22%;
    }                    
}