<div id="dropdown-1">
        <div class="heading">
      Click me
        </div>

            <ul class="content">
                <li><a href="#">Link</a></li>
                <li><a href="#">Link</a></li>
        </ul>
</div>

<div id="dropdown-2">
        <div class="heading">
      Click me
        </div>

            <ul class="content">
                <li><a href="#">Link</a></li>
                <li><a href="#">Link</a></li>
        </ul>
</div>

$(document).ready(function() {
    var openTabs = [];


    $(".content").hide();

    $(".heading").click(function(){
        var $this = $(this),
        selector = $this.parent().attr('id') + ' .heading';

        if ($(this).next('.content').is(':visible'))
        {
            var pos = openTabs.indexOf(selector);
            openTabs.splice(pos, 1);

        }
        else
        {

            openTabs.push(selector);
        }

        localStorage.openTabs = openTabs.join(',');

        $this.next(".content").slideToggle();

    });

    if (localStorage.openTabs)
        $(localStorage.openTabs).click();
});