Im using the wordpress theme "roots". If the width of the site is below 979px the navigation disappears and the tablet menu-button appears.
If you click on a dropdown-menu, the height of the navigation isn't calculated correctly at the first time. Only if you close the menu and reopen it, it works. At first I thought, this is my fault, but the official demo behaves the same: http://demo.rootstheme.com/
The problem appears in firefox 19, safari for windows, but not internet explorer.
This seems to be a js problem, but the js is minimized. Can that be fixed with CSS? (Maybe it depends on positioning or something). Am I the only one, who noticed this bug? I found nothing on the internet.