jQuery append not working in internet explorer

I have a jquery function that returns JSON data: This function works in Google Chrome, but not in Internet Explorer (v11).

$(document).ready(function () {

    $.ajax({
        url: "/../Projects/1/_vti_bin/ListData.svc/Prosjectlist?$select=ID,Tittel,Project_typeValue,Project_heading&$filter=(Project_typeValue%20eq%20%27Type1%27)", 
        method: "GET",
        dataType: "JSON",
        headers: { "accept": "application/json; odata=verbose" },
        success: function (data) {
            $('#projectRow').empty();

            $.each(data.d.results, function (index, item) {
                var itemExist = false;
                $.each($('.projectRow').find('h1'), function (index1, item1) {
                    if (item1.innerHTML == item.Project_heading) {
                        itemExist = true;
                        $(item1).parent().append("<h3><a id='" + item.ID + "' class='projectLink' href='#'>" + item.Title + "</a></h3>");

                    }
                });
                if (itemExist == false)
                    $('.projectRow').append("<div class='projectHeadingDiv left'><li><h1>" + item.Project_heading + "</h1><h3><a id='" + item.ID + "' class='projectLink' href='#'>" + item.Title + "</a></h3></div></li></div>");

            });           
        },
        error: function (error) {
            alert(JSON.stringify(error));
        }
    });

I am using jQuery 1.5.2 (Sharepoint 2010 gets fuzzy if I use anything newer). I have been looking at the debugger in IE11 and the data is there, it just won't append to my div. It seems that append might be the culprit, because if I replace .append() with .html() I can see the last item in the $each-loop. E.g:

$(item1).parent().html("<h3><a id='" + item.ID + "' class='projectLink' href='#'>" + item.Title + "</a></h3>");

Does anyone know why .append works in Chrome and not IE? The console doesn't give any error messages, and therefore no clues. However if I were to change "Document Mode" in IE dev tools from 8 (default) to 9 or higher, it appears to work as it should.

Any help is greatly appreciated.

You have two unmatched closing tags </div></li>. Fix HTML and it should work:

<div class='projectHeadingDiv left'><li><h1>" + item.Project_heading + "</h1><h3><a id='" + item.ID + "' class='projectLink' href='#'>" + item.Title + "</a></h3></div>

Chrome and Firefox are more forgiving to such careless of developers. But IE is more sensitive to this kind of errors (which I actually think good).