Path app copycat v2 with IE support

Make the navigation at least usable for IE8 and below users.

HTML

<nav>
    <!-- We don't really care about specific value of the input, but Opera doesn't trigger the state for this checkbox without it. -->
    <input type="checkbox" id="shownav" value="true" class="visuallyhidden" />
    <label for="shownav" class="ir">Show navigation</label>        
    <ul class="menu">
        <li><a href="#">1</a></li>
        <li><a href="#">2</a></li>
        <li><a href="#">3</a></li>
        <li><a href="#">4</a></li>
        <li><a href="#">5</a></li>
    </ul>
</nav>

CSS

/* Basics */
body {
    font-family: "Helvetica Neue", Helvetica, Arial, sans-serif;
    padding: .5em;
}
nav {
    background: #efede9;
    border: 1px solid #bfbeba;
    position: relative;
    width: 14em;
    height: 14em;
}        
/* Some helper classes from the HTML5 Boilerplate  */
html:not(.lt-ie9) .visuallyhidden { border: 0; clip: rect(0 0 0 0); height: 1px; margin: -1px; overflow: hidden; padding: 0; position: absolute; width: 1px; }
html:not(.lt-ie9) .ir { display: block; border: 0; text-indent: -999em; overflow: hidden; background-color: transparent; background-repeat: no-repeat; text-align: left; direction: ltr; *line-height: 0; }

/* The toggle */
input[type="checkbox"], label[for="shownav"] {
    /* we hide these elements from all browsers… */
    display: none
}
html:not(.lt-ie9) input[type="checkbox"],
html:not(.lt-ie9) label[for="shownav"] {
    /* … and show again for all modern browsers incl. IE9, but not IE8 and below */    
    display: block;
}
html:not(.lt-ie9) label[for="shownav"],
html:not(.lt-ie9) .menu {
    position: absolute;
    bottom: 5%;
    left: 5%;
    padding: 0;
    margin: 0;             
} 
html:not(.lt-ie9) label[for="shownav"],
html:not(.lt-ie9) .menu a {
    /* Basis for the circles */
    -webkit-border-radius: 50%;
    -moz-border-radius: 50%;
    border-radius: 50%;

    -moz-background-clip: padding;
    -webkit-background-clip: padding-box;
    background-clip: padding-box;

    -webkit-box-shadow: 0 0 0 3px #fff, 0 0 0 4px #949390, 0px .1em .15em 4px #bdbbb7;
    -moz-box-shadow: 0 0 0 3px #fff, 0 0 0 4px #949390, 0px .1em .15em 4px #bdbbb7;
    box-shadow: 0 0 0 3px #fff, 0 0 0 4px #949390, 0px .1em .15em 4px #bdbbb7;

}       
html:not(.lt-ie9) label[for="shownav"] {
    display: block;
    color: #fff;
    z-index: 2; /* to initially overlap the navigation items */
    height: 1em;
    width: 1em;
    line-height: 1;
    font-size: 2.4em;      
                
    background-color: #e76040;
   ...