website design - Keyboard shortcuts overriding default browser action

I'd like to add some keyboard shortcuts to my website. How severely is usability affected if I override the default browser behavior?

• CTRL+B: bolds the text instead of open bookmarks.


• CTRL+N: go to next step instead of opening new window.


• CTRL+P: play the video instead of printing.


• CTRL+R: refresh small portion of the page via AJAX instead of refresh the whole page


• CTRL+S: save your email, not the HTML

Rarely used browser operations

My personal opinion is that it's okay to override rarely used browser operations. I've never used CTRL+N to open a new window. I always press CTRL+T to open a new tab. I'm not the average user, so I'm not sure if opening a new window is more common than I think.

Common browser operations

CTRL+B is a tricky one. I see Stackexchange overrides bookmark opening with text bolding. I commonly use CTRL+B to open my bookmarks, so sometimes I get confused for a few milliseconds when it fails. On the other hand, CTRL+B is so common in text editors, such as Microsoft Word, that regular users would expect it to bold text, and not open the bookmarks.

Unconventional actions

Have there been any studies on what are the best keyboard shortcuts for certain operations? I noticed that there are conventions that most software follows. CTRL+E, for example, focuses the search engine box on browsers and focuses the search box on Windows Explorer. Could someone provide the conventions for the following?

• Play video: WMV uses CTRL+P, VLC uses spacebar.


• Stop video: VLC uses S, I only know CTRL+P to pause in WMV.


• Full screen video: WMV uses ALT+ENTER, VLC uses F.


• Next step: I believe ALT puts an underscore under the "n", then hitting N executes.


• Previous step: Probably the same as next, except with P.


• Delete item from list: ???


• Toggle a switch on or off: ???



• Select next item in list: Tab? But overriding it would prevent user from tabbing around to various HTML elements.

VLC Media Player has horrible UI compared with WMV, so I'm guessing I shouldn't follow their lead. It's been developed by computer programmers. I doubt they ever hired designers.

Answer

It can be more of an accessibility issue. Normal thought is to not break default browser behavior if you can avoid it.

Since keyboard commands tend to be used by power users, I'd suggest making this an option that can be set for those that want them. Something along the lines of 'enable keyboard shortcuts'.