Div confondu, mais pas partout

#div_gauche
{
z-index: 0;
}

#div_milieu
{
z-index: 5;
}

echo '<div class="menu"> .................. </div>';
	  	  
echo '<div class="bandeau">';
echo '<img src="images/village/images/13.jpeg" height="100"><img src="images/village/images/45.jpeg" height="100"><img src="images/village/images/40.jpeg" height="100"><img src="images/village/images/34.jpeg" height="100"><img src="images/village/images/41.jpeg" height="100"><img src="images/village/images/37.jpeg" height="100"><img src="images/village/album/images/41.jpeg" height="100"><img src="images/village/album/images/22.jpeg" height="100"><img src="images/village/images/22.jpeg" height="100">';
echo '<div class="titre1"><img src="images/kotoka2.jpg" height="80"></div>';
echo '<div class="titre1_1" style="position: absolute; background-color: #FFFFFF"><font color="#008000">&nbsp;ASSOCIATION  BRUMATH - KOTOKA</font></div>';
//echo '<div class="titre1_2" style="position: absolute; background-color: #FFFFFF"><font color="#33CC33">&nbsp;</font></div>';
echo '<div class="titre1_3" style="position: absolute; background-color: #FFFFFF"><font color="#800000">&nbsp;Président : Etienne WOLF</font></div>';
echo '<div class="titre1_4" style="position: absolute; background-color: #FFFFFF"><font color="#9933FF">&nbsp;« De l \' humanitaire oui, mais pas n\'importe comment ! »</font></div>';
echo '</div>';

echo '<div class="frame">';
include($inc);
echo '</div>';  


.menu {
position: absolute;
z-index: 0;
width: 160px;
height: 94%;
overflow: auto;
}
.bandeau {
margin-left: 12%;
height: 10%;
}
.frame {
margin-top: 20px;
margin-left: 160px;
margin-right: 3%;
height: 490px;
font-family: Comic sans MS, verdana, arial, helvetica, sans-serif;
overflow: auto;
}