Whats wrong with my drop down navigation menu? [possible ie issue]

Im trying to learn to build navigation menus using css. Ive stripped loads of tutorials down to the basics and got:

http://jsbin.com/osajiv/edit#html,live

When I mouse over the second link in fir开发者_如何学Pythonefox it drops down as expected however when I mouse over the link in ie it doesnt. Anyone know why this is?

Your style:

ul#nav:hover li ul
  {
    display: block;
  }

Change to

ul#nav li:hover ul
  {
    display: block;
  }

Jsfiddle: http://jsfiddle.net/thilakar/GYp74/