The web UI can now be navigated and controlled with a variety of hotkeys.
For example, 1-9 will focus a corresponding column (skipping the compose drawer, that is). n will focus the compose textarea, while alt+n will not only focus it but also reset it. s will focus the search form.
When a timeline is focused, j/down-arrow and k/up-arrow move the focus down/up; o/enter expands the status, p opens the author's profile, r to reply, m to mention author, f to favourite, b to boost.
In terms of general navigation, backspace is bound to navigating backward. A quick combination of g and certain letters will take you to a particular page: s to start, h to home, n to notifications, l to local timeline, t to federated timeline, f to your favourites, u to your own profile, p to your pinned toots, b to your blocked users, m to your muted users.
mastodon.to is one server in the network