+2  A: 

Maybe you could try changing the subnav class so that the 'top' declaration has an actual number value instead of just 'auto'

So maybe something like this...

.subnav { left:auto; top:59px; }
Sir David of Lee
This is close. You need to add top: 59px, but the left should be a defined pixel value since auto doesn't place it exactly where it needs to go. 0 will put it slightly to the left of where it falls when using auto in other browsers and IE8, so possibly left: 8px or so.
Mathachew
Good point, for some reason I missed in the example that if was off on the left as well.
Sir David of Lee
left: 0 works just fine, if its a few pixels off it doesn't matter, so long as it's under the top menu item and not way off to the right, I'm happy!
Adrian Trimble