Setting a div to display:none; using javascript or jQuery

On document ready do $("#yourId").hide();.

For example:

$(document).ready(function () {

     $("div.drill-down-wrapper").hide();
     var $drillDown = $("#drilldown");

        // (what ever your code is)
 });

Try this way:

$("#yourId").css("display","none");

it should work it!

I hope it helps.

Adding css value display:none to your css file works just fine. http://jsfiddle.net/dxkX6/4/

but I can see that you have a typo in your html file:

$("a.BNnavTrigger").click(function (event) {
       ^

<a class="BNavTrigger">Toggle Menu</a>
        ^

is that possibly the reason why you are experiencing the problem?