How do I reduce height of header?

Replies: 1

I would like to recude the height of the yellow box surrounding my drop-down menus. I’ve searched the forums and found CSS code, but when I paste code into the Customizing –> Additional CSS blank lines on the left, nothing changes. Either I don’t have the correct terminology, or there’s a trick to writing code (or adding to existing code) that I don’t know. I’m not a developer … I’m a speech therapist. !

This is what I’ve tried pasting in:

#nav {
min-height: 5px;
max-height: 15px
}
#supernav ul {
max-height: 15px;
line-height: 5px;
}
.main-navigation .main-nav ul li a {
line-height: 5px;
}