GreaseMonkey-DisableCtrlFHijacking.js

// ==UserScript==
// @name           Disable ctrl-F keyboard hijacking
// @description    Stop websites from highjacking keyboard shortcuts
//
// @run-at         document-start
// @include        *
// @grant          none
// ==/UserScript==

document.addEventListener('keydown', function(e) {
    // alert(e.keyCode); //uncomment to find out the keycode for any given key
    if (e.ctrlKey && (e.keyCode == 70))
    {
        e.cancelBubble = true;
        e.stopImmediatePropagation();
    }
    return false;
});