bei "height" wird submenü überlagert

[schlurpsel]

Hey Leute,

habe eine Webseite erstellt: Voice of music.
Dort gibts links ein Menü, bei dem man unter Galerie zwei Unterpunkte hat. Die zwei Unterpunkte bei Galerie werden von den Oberpunkten, die darunter sind, im IE7 und Firefox überlagert, wenn ich für den li-Tag eine "height" angebe. Gebe ich keine height an, sieht das ganze im IE6 und IE7 sehr komisch aus (Voice of music).

Was kann ich machen, dass das Submenü nicht überlagert wird, aber trotzdem alles richtig angezeit wird?

Hier noch das .css-file:

@charset "utf-8";
/* css voice-of-musik */
body {
 margin-left: 0px;
 margin-top: 50px;
 margin-right: 0px;
 margin-bottom: 0px;
 background: #7976A8;
 font-family:arial;
 font-size:12px;
 color:black;
}
a {color:black; cursor:hand; cursor:pointer;}
.header {background:url(logo-vom.png) no-repeat;}
table {padding:0px;}

.nav {padding:0px; margin:0px;}
.nav ul {padding:0; margin:0;}
 
 
/* hier mit oder ohne height*/
.nav ul li { list-style:none;  margin:0px; margin-left:10px; padding:0px; border-bottom:1px solid #cccccc;}
 
 
 
.nav ul li a { height:25px; padding:0; margin:0; line-height:25px; color:black; text-decoration:none; }
.nav ul li a div {width:130px;}
.nav ul li a:hover {color:orange;}
.nav ul li a.mark {color:#e77817;}
.nav ul li a:hover img.normal {display:none;}
.nav ul li a:hover img.over { display:block;}
.nav ul li a img.over { display:none; }
.nav ul li a img.overm { display:block;}
.nav ul li a img.normalm {display:none;}

.nav ul li ul li {border: none;}
.nav ul li ul li a {list-style:none; line-height:20px; height:20px; margin:0px; padding:0px; border:none;}
.nav ul li ul li a div {width:100px;}
.nav ul li ul { display:none;}
.nav ul li ul.mark {display:block;}
.nav ul li ul li a:hover {color:orange;}
.nav ul li ul li a.mark {color:#e77817}
.main {padding:0; margin:0; padding-bottom:10px; padding-right:40px;}
.main h1 { padding:0; padding-top:0px; padding-bottom:10px; margin:0;}

noch die nav.php

<ul>
<li id="none"><!--[if IE 6]><li style="height:25px;"><![endif]--><a class="<?php if ($nav == 'aktuelles') {echo 'mark';} else {} ?>" href="index.php?nav=aktuelles&main=aktuelles"><img class="normal<?php if ($nav == 'aktuelles') {echo 'm';} else {} ?>" src="style/pfeil1.png" border="0" style="float:left;padding-top:8px;" /><img class="over<?php if ($nav == 'aktuelles') {echo 'm';} else {} ?>" src="style/pfeil1on.png" border="0" style="float:left;padding-top:8px; " /><div >&nbsp;&nbsp;Aktuelles</div></a></li>
<li id="none"><!--[if IE 6]><li style="height:25px;"><![endif]--><a class="<?php if ($nav == 'termine') {echo 'mark';} else {} ?>" href="index.php?nav=termine&main=termine"><img class="normal<?php if ($nav == 'termine') {echo 'm';} else {} ?>" src="style/pfeil1.png" border="0" style="float:left;padding-top:8px;" /><img class="over<?php if ($nav == 'termine') {echo 'm';} else {} ?>" src="style/pfeil1on.png" border="0" style="float:left;padding-top:8px; " /><div >&nbsp;&nbsp;Termine</div></a></li>
<li id="none"><!--[if IE 6]><li style="height:25px;"><![endif]--><a class="<?php if ($nav == 'ueber_uns') {echo 'mark';} else {} ?>" href="index.php?nav=ueber_uns&main=ueber_uns"><img class="normal<?php if ($nav == 'ueber_uns') {echo 'm';} else {} ?>" src="style/pfeil1.png" border="0" style="float:left;padding-top:8px;" /><img class="over<?php if ($nav == 'ueber_uns') {echo 'm';} else {} ?>" src="style/pfeil1on.png" border="0" style="float:left;padding-top:8px; " /><div >&nbsp;&nbsp;&Uuml;ber uns</div></a></li>
<li id="none"><!--[if IE 6]><li style="height:25px;"><![endif]--><a class="<?php if ($nav == 'galerie') {echo 'mark';} else {} ?>" href="index.php?nav=galerie&main=galerie"><img class="normal<?php if ($nav == 'galerie') {echo 'm';} else {} ?>" src="style/pfeil1.png" border="0" style="float:left;padding-top:8px;" /><img class="over<?php if ($nav == 'galerie') {echo 'm';} else {} ?>" src="style/pfeil1on.png" border="0" style="float:left;padding-top:8px; " /><div>&nbsp;&nbsp;Galerie</div></a>
<ul style="z-index:10;" class="<?php if ($nav == 'galerie') {echo 'mark';} else {} ?>" href="index.php?nav=galerie&main=galerie">
<li id="none"><!--[if IE 6]><li style="height:20px;"><![endif]--><a class="<?php if ($nav1 == 'bilder') {echo 'mark';} else {} ?>" href="index.php?nav=galerie&nav1=bilder&mainp=galerie"><img class="normal<?php if ($nav1 == 'bilder') {echo 'm';} else {} ?>" src="style/pfeil1.png" border="0" style="float:left;padding-top:6px;" /><img class="over<?php if ($nav1 == 'bilder') {echo 'm';} else {} ?>" src="style/pfeil1on.png" border="0" style="float:left;padding-top:6px; " /><div >&nbsp;&nbsp;Bilder</div></a></li>
<li id="none"><!--[if IE 6]><li style="height:20px;"><![endif]--><a class="<?php if ($nav1 == 'tonbeispiele') {echo 'mark';} else {} ?>" href="index.php?nav=galerie&nav1=tonbeispiele&main=galerie/ton"><img class="normal<?php if ($nav1 == 'tonbeispiele') {echo 'm';} else {} ?>" src="style/pfeil1.png" border="0" style="float:left;padding-top:6px;" /><img class="over<?php if ($nav1 == 'tonbeispiele') {echo 'm';} else {} ?>" src="style/pfeil1on.png" border="0" style="float:left;padding-top:6px; " /><div >&nbsp;&nbsp;Tonbeispiele</div></a></li>
</ul></li>
<li id="none"><!--[if IE 6]><li style="height:25px;"><![endif]--><a class="<?php if ($nav == 'kontakt') {echo 'mark';} else {} ?>" href="index.php?nav=kontakt&main=kontakt"><img class="normal<?php if ($nav == 'kontakt') {echo 'm';} else {} ?>" src="style/pfeil1.png" border="0" style="float:left;padding-top:8px;" /><img class="over<?php if ($nav == 'kontakt') {echo 'm';} else {} ?>" src="style/pfeil1on.png" border="0" style="float:left;padding-top:8px; " /><div >&nbsp;&nbsp;Kontakt</div></a></li>
<li id="none"><!--[if IE 6]><li style="height:25px;"><![endif]--><a class="<?php if ($nav == 'impressum') {echo 'mark';} else {} ?>" href="index.php?nav=impressum&main=impressum"><img class="normal<?php if ($nav == 'impressum') {echo 'm';} else {} ?>" src="style/pfeil1.png" border="0" style="float:left;padding-top:8px;" /><img class="over<?php if ($nav == 'impressum') {echo 'm';} else {} ?>" src="style/pfeil1on.png" border="0" style="float:left;padding-top:8px; " /><div >&nbsp;&nbsp;Impressum</div></a></li>
<li id="none"><!--[if IE 6]><li style="height:25px;"><![endif]--><a target="blank" href="files/noten/noten.php"><img class="normal<?php if ($nav == 'intern') {echo 'm';} else {} ?>" src="style/pfeil1.png" border="0" style="float:left;padding-top:8px;" /><img class="over<?php if ($nav == 'intern') {echo 'm';} else {} ?>" src="style/pfeil1on.png" border="0" style="float:left;padding-top:8px; " /><div >&nbsp;&nbsp;Intern</div></a></li>
</ul>
<br />
<br />
<br />

schonma danke für die Hilfe
schlurpsel