Webapp Keyboard Focus Issues

I've found a pretty frequent problem with keyboard-enabled webapps. Gmail, Google Reader, Remember The Milk, and a whole bunch of other services (Google Calendar, for instance) all fit into this category.

It seems that nearly all keyboard shortcut-enabled webapps have one big annoyance in common (no, not AJAX): The shortcuts lose focus in certain scenarios.

The three apps I'm most concerned with are, of course, Gmail, Google Reader, and RTM. I do use them the most, after all.

I've found tab-switching to be the number one cause of focus switching. Keyboard entry is sent to the browser chrome or something, rather than the page. I've noticed that switching tabs with the keyboard (using Firefox's Ctrl+Tab and Ctrl+Shift+Tab keystrokes) is much less likely to cause a problem than clicking the other tab.

At this point, I should mention that I haven't checked other browsers for trouble; I've only been observing Firefox 2.0.0.x.

Yet, the problem does not seem to be webapp-specific. I have trouble with Home, Page Down, Page Up, and End when switching tabs, too. I'll switch to a new tab, hit Home or End (usually), and nothing will happen. I go back to the previous tab and find that the keypress was actioned there. Harrumph.

I really have no idea whose problem this is -- app developers' or Mozilla's -- but it's certainly annoying. When I'm trying to copy data from one site to another, without a clean import/export interface, I would prefer to not have to click in the page to get the shortcuts to work again.

Anybody have a definitive answer as to why this happens?