Create a button that will toggle the menu:
var menuEnabled = false;
$("button").click(function() {
if (menuEnabled) {
$("#left").css("display", "none");
$("#content").css("margin-left", "0");
menuEnabled = false;
} else {
$("#left").css("display", "block");
$("#content").css("margin-left", "200px");
menuEnabled = true;
}
});
Full Demo here: http://jsfiddle.net/YwRSb/4/