It's worth recalling that in the early days, GUIs always had underlined letters showing what the keyboard shortcuts are. That's been lost now, I suppose because it looked messy or confused people or something. Some tools show you the underlines only once you push the modifier key that can activate them.

Unfortunately, one of the many shortcomings of the web as an application and GUI platform is (a) no menu bars, (b) no context menus, (c) no accelerator key framework, (d) keyboard focus is often nowhere in particular or somewhere stupid that will do something bad if you touch the keys.