problem s css menu

Muzete mi prosim pomoci, proc se subodkazy ktere vyjedou nezobrazuji primo pod hlavnim odkazem (v mozile to funguje ale v IE ne).

http://matata.wz.cz/rr

css:

/* menu */
ul#mainMenu, ul
{
color:000000;
font-size:12px;
padding-left:0;
margin:0;
list-style-type:none;
text-transform: uppercase;
text-align:center
}

ul#mainMenu ul
{
margin-top:0px;
}
/* hlavni odkazy bez URL */
ul#mainMenu li
{
float:left;
padding-left:0px;
width:150px;
color:black;
background-color:#dddddd;
display:block;
text-decoration:none;
font-weight:bold;
}
/* hlavni odkazy s URL */
ul#mainMenu a
{
color:black;
background-color:#dddddd;
display:block;
border-bottom:3px solid white;
text-decoration:none;
font-weight:bold;
}

ul#mainMenu a:hover
{
color:yellow;
background-color:#dddddd;
display:block;
border-bottom:3px solid white;
text-decoration:none;
font-weight:bold;
}
/* vedlejsi odkazy s URL */
ul#mainMenu ul a
{
border-bottom:none;
border-left:1px solid #dddddd;
border-right:2px solid #dddddd;
padding-left:2px;
}

ul#mainMenu ul a:hover
{ color:pink;
border-left:5px solid red;
border-right:1px solid blue;
background-color:#ffffff;
}

ul#mainMenu ul
{
position:absolute;
visibility:hidden;
border-bottom:1px solid white;
background-color:white;
}

ul#mainMenu li:hover ul, ul#mainMenu li.hover ul
{
visibility:visible;
}

ul#mainMenu li li
{
float:none;
border:none;
padding:0;
}

ul#mainMenu li
{
behavior: url(hover.htc);
}