layer with div's doesn't show on IE9

-- part of html page:
                <div id="mainbackground">
            <img src="images/home/background.png" id="mainbackgroundimage"/>


                <!-- 6 divs for hover/clickable areas -->
                <div id="infojarne">
                    <img src="images/home/infojarne.gif" id="inforjaneImg">
                </div>
                <div id="paintings">
                    <img src="images/home/paintings.gif" id="paintingsImg">
                </div>
                <div id="etc">
                    <img src="images/home/etc.gif" id="etcImg">
                </div>
                <div id="projects">
                    <img src="images/home/projects.gif" id="projectsImg">
                </div>
                <div id="digitalart">
                    <img src="images/home/digitalart.gif" id="digitalartImg">
                </div>
                <div id="drawings">
                    <img src="images/home/drawings.gif" id="drawingsImg">
                </div>

        </div>

--Javascript file to set positioning:

// because ie does not support console if not in debug...
if (!window.console) console = {log: function() {},info: function(){}};

$("document").ready(function(){

    function ImageDimensions (width, height, x, y, id){
        this.width = width;
        this.height = height;
        this.x = x;
        this.y = y;

        if(id){
            var $div = $(id);
            $div.css("z-index", "1");
            if(id == "#etc"){
                $div.css("right", "0px");
                $div.css("bottom", "0px");
            }else{
                $div.css("left", this.x +"px");
                $div.css("top", this.y +"px");
            }

            $div.css("width", this.width +"px");
            $div.css("height", this.height +"px");
            $div.hover(
                function(event){
                    $div.find("img").show();
                },
                function(event){
                    $div.find("img").hide();
                }
            );
            $div.click(function(){
                var location;
                if($div.attr("id") == "infojarne"){
                    $(window.location).attr('href', 'infojarne.html');
                }if($div.attr("id") == "digitalart"){
                    $(window.location).attr('href', 'digitalart.html');
                }else{
                    console.info("unknown id : " + id);
                }
            });
            var $imgObj = $(id+ " img");
            $imgObj.hide();
        }
    };

    var background = new ImageDimensions(836, 638);
    // TODO on resize recalc this + reposition
    var windowWidth = $(window).width();
    console.info("windowWidth:" + windowWidth);
    var leftMargin = (windowWidth - background.width) /2;
    console.info("left margin:" + leftMargin);

    $("#mainbackground").css("left",leftMargin+"px");
    $("#mainbackground").css("z-index","0");


    var infojarne = new ImageDimensions(413, 200, 149, 0, "#infojarne");
    var drawings = new ImageDimensions(272, 138, 0 ,200, "#drawings");
    var digital = new ImageDimensions(276, 172, 0, 338, "#digitalart");
    var projects = new ImageDimensions(311, 128 ,276, 509, "#projects");
    var etc = new ImageDimensions(249, 299, 587, 340, "#etc");
    var paintings = new ImageDimensions(290, 138, 546, 200, "#paintings");

});


DESCRIPTION OF CODE (WHAT AM I TRYING TO ACHIVE):
*. set the encapsulating div "mainbackground" in the center of the screen.(position relative) + set the width and height of the div. This equals the dimensions of the background image "#mainbackgroundimage"

*. the containing divs should react on hovers, and show the image that they hide when the div is hovered.
Therefore i have set the divs width and height and position so the hover can happen, and hidden the image contained in that div.

PROBLEM:
For some reason this does not work on IE9. It works however on FireFox and Chrome.
I have tried some stuff with the z-index but at no avail ...
Can anybody shed some light on this issue