Test page.
In this page Opera shouldn't show its normal context menu, and instead use only our own code
In order to debug something in Opera, remember to use Opera.postError()
I've only bothered to make it work in Opera, as we know that the rest of the browsers handle the
oncontextmenu event and it can be cancelled properly
In Mac, Opera does raise an oncontextmenu event, but it can't be cancelled, so we must ignore it
(that's why I'm attaching the property "synthetic" to use only our custom event and don't mess
with the original one or the default menu will be shown)
To be able to test the page you must have javascript enabled and in the preferences, advanced, content, javascript options, "Allow script to receive right clicks" must be checked (it's off by default)
This script only takes care of the context menu generated by the mouse. The keyboard won't be affected.
We listen to the event with " addEventListener('contextmenu', showmenu, false);". It's possible to make it work also with "oncontextmenu = showmenu ;", but I don't think that we need to care about that.