Suddenly I found answer here
You should add “?” to your favicon path and it works! Even with path such as images/favicon.ico. Just try:
<link rel="icon" href="https://stackoverflow.com/images/favicon.ico?" type="image/x-icon">
Other browsers works too.
Remember to restart mozilla, because of it’s own cache, that is not connected with css and other caching.
updated:
Another way is set redirect from favicon.ico to /images/favicon.ico (301 works)