I have a webapp which will be viewed using certain popular browsers and I am required to support the handling of certain keypress events. Our users will be using Windows and the keypress events always use the `Alt` key as a modifier.

There is no specific requirement for keyUp/keyDown event handling, the user just has to feel like something happens when he/she presses, for example, `Alt`-`F`.

**How do we accomplish this in the Firefox browser, which we are required to support?**

**The problem:**
All of our implementation attempts are interfered-with by the fact that when the FireFox menu bar is visible (File, Edit...), pressing an `Alt` key combination which is already claimed by the menu bar (example: `Alt`-`f`) will cause the appropriate menu to expand. We don't want this to happen. I have been shown examples of web apps (using tens of thousands of lines of javascript....) that do NOT experience this issue, so I know it is possible, but I don't know how this was done in the example I've seen with my own eyes.

I can find dozens of examples on the web of how to write an alt-key handler in JS, but I haven't found a single article on this issue or a single code example that works under the circumstances I've described. We are using Spring-MVC and a recent version of jQuery, if that matters. 

I'm happy to update the question with any other information that proves relevant.

Side note about work-around suggestions:  

The requestor has specifically demanded that I use the Alt key as the modifier, on the grounds that they use other webapps in FireFox where both the menu-bar is visible AND `alt` key combinations work. (Example: `Alt`-`s`). So, feel free to post well-intentioned work-arounds in the comment section if you wish - I promise that my own personal curiosity will drive me to read them all - but also keep in mind this is not the subject of my question.