Hover on menu disappears when using background slider with position:fixed and z-index

Question

I found out that the hover effect from the main menu disappears if I want to go to the second menu level. Here you find the example:

http://bfb.bplaced.net/ie/

HTML:

<div id="background-slider">
    <a href="http://www.hdwallpapersarena.com/wp-content/uploads/2012/10/Opera-Background-Blue-Swirls.jpg"></a>
    <a href="http://www.hdwallpapersarena.com/wp-content/uploads/2012/10/green-abstract-background.jpg"></a>
</div>
<div id="menu">
    <nav>
        <ul class="nav-level-1">
            <li class="level-1 clearfix">
                <a href="unternehmen.html" class="level-1">Unternehmen</a>
                <ul class="nav-level-2">
                    <li class="level-2"><a href="/unternehmen/die-firma.html" class="level-2">Die Firma</a></li>
                    <li class="level-2"><a href="/unternehmen/das-team.html" class="level-2">Das Team</a></li>
                    <li class="level-2"><a href="/unternehmen/allgemeines.html" class="level-2">Allgemeines</a></li>
                </ul>
            </li>
        </ul>
        <div class="clearer"></div>
    </nav>
</div>
<div id="script-section" class="hidden">
    <script src="./js/jquery.superbgimage.min.js"></script>
    <script>
        $(document).ready(function(){
            // Options for SuperBGImage
            $.fn.superbgimage.options = {
                transition: 1,
                speed: 'slow',
                randomtransition: 0,
                slideshow: 1,
                slide_interval: 6000,
                randomimage: 0
            };

            // initialize SuperBGImage
            $('#background-slider').superbgimage().hide;
        });
    </script>
</div>

CSS:

#menu {
    position: fixed;
    z-index: 4;
    left: 23px;
    bottom: 40px;
}

ul.nav-level-1 {
    float: left;
    text-align: left;
}

ul.nav-level-1 li.level-1 {
    /*float: left;*/
}

ul.nav-level-1 li.level-1 a.level-1 {
    font-family: 'SourceSansProBlack', Arial, sans-serif;
    font-size: 36px;
    line-height: 40px;
    text-transform: uppercase;
    text-decoration: none;
    color: #123373;
    padding: 0 5px;
    transition: color 0.25s ease 0s, background-color 0.25s ease 0s;
    float: left;
}

ul.nav-level-1 li.level-1 a.level-1:hover {
    text-decoration: none;
    color: #123373;
    background-color: #FFF;
    display: inline-block;
}

ul.nav-level-1 li:hover a {
    background-color: #FFF;
}

ul.nav-level-1 li.level-1:hover ul.nav-level-2 {
    display: block;
}

ul.nav-level-2 {
    display: none;
    float: left;
    width: 390px;
    padding-left: 10px;
    text-align: left;
}

ul.nav-level-2  li.level-2 {
    margin-bottom: 3px;
    margin-right: 5px;
    float: left;
}

ul.nav-level-2  li.level-2 a.level-2{
    font-family: 'SourceSansProBold', Arial, sans-serif;
    font-size: 14px;
    line-height: 16px;
    text-transform: uppercase;
    text-decoration: none;
    color: #123373;
    padding: 0 5px;
    background-color: #FFF;
    transition: color 0.25s ease 0s, background-color 0.25s ease 0s;
}

ul.nav-level-2  li.level-2 a.level-2:hover{
    background-color: #123373;
    color: #FFF;
}

The slider I'm using is called SuperBGImage. If I remove the slider everything works!

I thin it's the z-Index bug of IE but I tried different options by adding position: relative; without success. How do I get the hover effect fixed in IE?

I tried this JS code but it doesn't help either:

$('li.level-1').hover(function() {
    $(this).children('ul.nav-level-2').removeClass('hidden');
    $(this).children('ul.nav-level-2').addClass('visible');
});
$('ul.nav-level-2').mouseout(function() {
    $(this).removeClass('visible');
    $(this).addClass('hidden');
});

Perhaps it is a float issue. If I remove float: left; than it works better but it is not the design which it should be.

Edit:

Here you can download the project. I noticed another thing. If I start the Internet Explorer he asks me if I want to start the scripts or the Active-X elements. Why does he ask me that? I know it's because the slider but it should be normal Javascript. Perhaps the JS from the slider does something special here ...

Answer 1

I've got it working on IE9 & IE10 should also work in IE8, using transparent background and hovering over .clearfix

Check out the updated - jsFiddle

I changed this-

ul.nav-level-1 li.level-1 a.level-1:hover {
    text-decoration: none;
    color: #123373;
    background-color: #FFF;
    display: inline-block;
}

To this-

.clearfix:hover ul.nav-level-1, li.level-1, a.level-1{
    text-decoration: none;
    color: #123373;
    background: rgba(0, 0, 0, 0.0); /*** TRANSPARENT BACKGROUND FIX ***/
    display: inline-block;
}

And added height and width to this-

.clearfix {
    display:block;
    width:100%;    /* added height and width */
    height:50px;
}

for IE7 and below add-

<!--[if lte IE 7]>
    <style type="text/css">
 .clearfix:hover ul.nav-level-1, li.level-1, a.level-1 {
    text-decoration: none;
    color: #123373;
    background:#ffffff;
    display: inline-block;
}
    </style>
<![endif]-->

The above work around just replaces the transparent rgba with a solid white. It wont be as pretty in ancient IE, but few things ever are.

Note, that <nav> isn't supported in IE8 and below