Error in secondary-menu with IE

hello,

I see a problem with the secondary with float left.
I change this code in style.css:
#navigation ul.secondary-menu li {
margin: 0;
padding: 0;
}
#navigation ul.secondary-menu li a {
display: block;
line-height: 18px;
padding: 0 5px;
border-right: solid 1px black;
float: left;
}
by this code :
#navigation ul.secondary-menu li {
margin: 0;
padding: 0;
float: left;
}
#navigation ul.secondary-menu li a {
display: block;
line-height: 18px;
padding: 0 5px;
border-right: solid 1px black;
}

Now the secondary-menu is ok.