clearfix

.columnlist {
    margin-left: 0px;
}

    .columnlist::after {
        /*clearfix*/
        content: "";
        display: block;
        clear: both;
    }

    .columnlist > * {
        margin-left: 0px;
        display: block;
        width: auto;
        float: none;
    }

@media (min-width: 1000px) {
    .columnlist > * {
        float: left;
        width: 25%;
    }
}