Twenty eleven centered navigation don't work in firefox help

Hello ??

I’m working on a website https://cantanta.dk/trendnu

and I’ve used this code in my childtheme on Twenty Eleven to center the navigation:

.menu {
overflow: hidden;
}
.menu ul {
overflow: hidden;
text-align: center;
}
.menu li{
display: inline-block;
float: none !important;
}

– somehow it works in chrome and safari, but it wont center in firefox. I have tried with firebug, but I can’t figure it out. Anyone? ??

Nina