HTML:

<div class="gleich">
    <div class="row">
        <div class="one"></div>
        <div class="two"></div>
        <div class="three"></div>
    </div>
</div>

CSS:

.gleich {
    display:table;
}
.row {
    display:table-row;
}
.row div {
    display:table-cell;
}

function showhide(e) {
el = document.getElementById(e);
el.style.display = el.style.display == "none" ? "" : "none";
}