@media (max-width: 1000px) {

    #grid {
    -moz-column-count: 2;
    -webkit-column-count: 2;
    column-count: 2;
    }
}
@media (max-width: 800px) {
    #grid {
    -moz-column-count: 1;
    -webkit-column-count: 1;
    column-count: 1;
    }
}