Firefox Bookmarks Auto-hide

The CSS below auto-hides the bookmark bar on new tabs like how Google Chrome does it. Got it from this Reddit post. Just copy and paste to your userChrome.css file.

.tab-close-button:not([pinned="true"]) { display: -moz-box !important; }
#PersonalToolbar {
visibility:collapse;
}

#main-window[title^="New Tab"] #PersonalToolbar,
#main-window[title="Mozilla Firefox"] #PersonalToolbar {
visibility:visible !important;
}

UPDATE: A better Chrome-like implementation of the auto-hiding bookmark toolbar:

#main-window #PersonalToolbar {
visibility: collapse !important;
}
#main-window[title^="about:newtab"] #PersonalToolbar,
#main-window[title^="New Tab"] #PersonalToolbar,
#main-window[title^="Nightly"] #PersonalToolbar,
#main-window[title^="Mozilla Firefox"] #PersonalToolbar,
#main-window[title^="Firefox"] #PersonalToolbar {
visibility: visible !important;
}