ToggleById

<script type="text/javascript">
    function toggleById(id) {
        var element = document.getElementById(id);
        if (element.style.display == "none")
            element.style.display == "block";
        else
            element.style.display = "none";
    }
</script>

//DECLENCHEUR
<div onclick="toggleById('MaDivCacher')">

</div>

//ELEMENT CACHER
<div id="MaDivCacher" style="display: none;">

</div>