title: How to disable Ctrl C/V using javascript for both internet explorer and firefox browsers
body: <p>I am making this javascript code in order to disable Ctlr+c and Ctlr+v, prenscreen, ALT+TAB, Ctlr+S, and PrintScreen keys.</p>
  
  <pre><code>&lt;html&gt;
  &lt;head&gt;
  &lt;script language="javascript"&gt;
  
  function Disable_Control_C() {
  var keystroke = String.fromCharCode(event.keyCode).toLowerCase();
  
  if (event.ctrlKey &amp;&amp; (keystroke == 'c' || keystroke == 'v')) {
  alert("let's see");
  event.returnValue = false; // disable Ctrl+C
  }
  }
  
  &lt;/script&gt;
  &lt;/head&gt;
  &lt;body onkeydown="javascript:Disable_Control_C()"&gt;
  Hello World!
  &lt;/body&gt;
  &lt;/html&gt;
  </code></pre>
  
  <p>unfortunately, code is working on IE browser, but not working on firefox. Can anyone here advice?</p>