First of all thank you for this theme, I really like it and it does it's job perfectly. It's nice and clean and simple.
That said I'm encountering an issue with the behaviour of the menu bar in Firefox, where the menu is shorter than in both Chrome and IE10 and it doesn't follow the page when you scroll. This is both on my own blog and on your own website.
I've tried looking around in the CSS files of the theme, but I haven't been able to find out why it's different in Firefox, but I guess it's because it renders the menu differently than in other browsers.
Do you have any ideas where I should look to correct this behaviour? You don't have to come up with the solution, just maybe point me in the right direction to where I have to look. Maybe it's not in the CSS, but in some of the functions of the theme?