IE und Firefox Darstellungsprobleme

<div id="navigation">
            <ul>
                <li id="home"><a href="home.html"><div class="navi"></div></a></li>
                <li id="_2d"><a href="2d/2d.html"><div class="navi"></div></a></li>
                <li id="_3d"><a href="3d/3d.html"><div class="navi"></div></a></li>
<li id="cut_vfx"><a href="cut_vfx/cut_vfx.html"><div class="navi"></div></a></li>
                <li id="sound"><a href="sound/sound.html"><div class="navi"></div></a></li>
<li id="kontakt"><a href="kontakt/kontakt.php"><div class="navi"></div></a></li>
<li id="impressum"><a href="impressum.html"><div class="navi"></div></a></li>
                   <li id="fuss"><div class="fuss"></div></li>
            </ul>
        </div>




Und der Validator sagt: 


[I]Line 19, Column 68[/I]: document type does not allow element "div" here; missing one of "object", "applet", "map", "iframe", "button", "ins", "del" start-tag … id="home"><a href="home.html"><div class="navi"[B]>[/B]</div></a></li>           [URL='http://validator.w3.org/feedback.html?uri=http%3A%2F%2Fwww.xiller.de%2Fdesign%2Fhome.html;errmsg_id=65#errormsg']✉[/URL]     
The mentioned element is not allowed to appear in the context in which you've placed it; the other mentioned elements are the only ones that are both allowed there [I]and[/I] can contain the element mentioned. This might mean that you need a containing element, or possibly that you've forgotten to close a previous element. 
 One possible cause for this message is that you have attempted to put a block-level element (such as "<p>" or "<table>") inside an inline element (such as "<a>", "<span>", or "<font>"). 






Und das eben auch die anderen "Buttons" betreffend. Ich habe auch schon das div entfernt und einfach mal ein zum Ausprobieren das <del> Tag genommen, aber im IE unter 8.0 klappts einfach immernoch nicht.




Ausschnitt CSS Stylesheet:
#navigation 
{
    width:430px;
    background-color:#000;
    float:left;
    margin:0px;
    color:#000;
    padding:0;
}
#content
{
    width:700px;
    height:700px;
    margin:auto auto auto 350px;
}


#main_content
{
    width:660px;
    height:660px;
    margin-left:50px;
    margin-top:20px;
    position:absolute;


    
}






ul
{
    list-style:none;
}
li
{
    margin-left:-25px;
}
.navi
{
    width:311px;
    height:60px;
}
#home
{
    background: url(../menu/2D_6_1_01.jpg) #000;
    width:311px;
    height:60px;
    border:none;


}
#home a:hover
{
    background:url(../menu/hover/2D_7_01.jpg) #000;
    width:311px;
    height:60px;
    color:#000;
    display:block;
    border:none;
}
#_2d
{
    background:url(../menu/2D_6_1_03.jpg) #000;
    width:311px;
    height:60px;
    border:none;
} 
#_2d a:hover
{
    background:url(../menu/hover/2D_7_03.jpg) #000;
    width:311px;
    height:60px;
    display:block;
    color:#000;
    border:none;
}
#_3d
{
    background:url(../menu/2D_6_1_04.jpg) #000;
    width:311px;
    height:60px;
    border:none;
}
#_3d a:hover
{
    background:url(../menu/hover/2D_7_04.jpg) #000;
    width:311px;
    height:60px;
    display:block;
    color:#000;
    border:none;
}
#cut_vfx
{
    background:url(../menu/2D_6_1_05.jpg) #000;
    width:311px;
    height:60px;
    border:none;
}
#cut_vfx a:hover
{
    background:url(../menu/hover/2D_7_05.jpg) #000;
    width:311px;
    height:60px;
    display:block;
    color:#000;
    border:none;
}
#sound
{
    background:url(../menu/2D_6_1_06.jpg) #000;
    width:311px;
    height:60px;
    border:none;
}
#sound a:hover
{
    background:url(../menu/hover/2D_7_06.jpg) #000;
    width:311px;
    height:60px;
    display:block;
    color:#000;
    border:none;
}
#kontakt
{
    background:url(../menu/2D_6_1_07.jpg) #000;
    width:311px;
    height:60px;
    border:none;
}
#kontakt a:hover
{
    background:url(../menu/hover/2D_7_07.jpg) #000;
    width:311px;
    height:60px;
    display: block;
    color: #000;
    border:none;
}
#impressum
{
    background:url(../menu/2D_6_1_08.jpg) #000;
    width:311px;
    height:60px;
    border:none;
}
#impressum a:hover
{
    background:url(../menu/hover/2D_7_08.jpg) #000;
    width:311px;
    height:60px;
    display: block;
    color: #000;
    border:none;
}
.fuss
{
    background:url(../menu/2D_6_1_09.jpg) #000;
    width:423px;
    height:252px;
}