Disable_Ctrl.user.js

// ==UserScript==
// @name         Disable Ctrl
// @description  Stops websites from stealing Ctrl keys
// @run-at       document-start
// @include      *
// @match        https://*/*
// @match        http://*/*
// @grant        none
// ==/UserScript==
/* jshint -W097 */
'use strict';

var func = function(e) {
    //console.log(e.keyCode);
    // C-d, C-h, and C-l (u == 85)
    var ignore = [68, 72, 76];
    if ((e.ctrlKey || e.metaKey) && ignore.indexOf(e.keyCode) == -1) {
        e.cancelBubble = true;
        e.stopPropagation();
        e.stopImmediatePropagation();
        //console.log('Captured!');
    }
    return false;
};
(window.opera ? document.body : document).addEventListener('keypress', func, !window.opera);
(window.opera ? document.body : document).addEventListener('keydown', func, !window.opera);