title: Web page: detect and block certain keyboard shortcuts
body: <p>I want to detect and block certain keyboard shortcuts on a web page. For example, say I want to prevent <kbd>alt</kbd>+<kbd>tab</kbd> for switching apps (just an example, assume any global shortcut).</p>
  <p>Here's as far as I can think it out:</p>
  <ul>
  <li>attach a keyboard event listener to
  <code>document</code> (or <code>window</code>?)</li>
  <li>use <code>event.which</code> to check which key
  combination was pressed</li>
  <li>if it was a blacklisted shortcut,
  stop the browser from executing it</li>
  </ul>
  <p>But, I don't know how to<br />
  <strong>A) detect <em>multiple keys</em></strong> (e.g. <kbd>alt</kbd> and <kbd>tab</kbd> together), or<br />
  <strong>B) stop them from executing</strong> (can I just <code>return false</code>?).</p>
  <p>Can anyone tell me how to accomplish the above?</p>