Question: [Problem](https://bugzilla.mozilla.org/show_bug.cgi?id=519028) exists only on FireFox (from 3.6 up to current 9), other browsers are fine. My code looks like this:

```
jQuery.extend({
    AnchorFromUrl : function(url) {
        var anchor = url.substr(1).replace('.html','');
        $.fizzer_anchor = anchor;
        window.location.hash = anchor;
        return anchor;
    }
});

```

The most weird thing is that if I place an alert before the window.location.hash = anchor; line, after clicking Ok favicon doesn't disappear, remove that alert() and you get your favicon disappearing.

Note: it also drops the favicon if you just do `window.location = something`.

Answer: 
I had the same problem, but found this interesting post and it worked for me, its just adding 2 lines of javascript.
The problem occure when the hash element changes, so, we need to re-stablish it via javascript

<http://kilianvalkhof.com/2010/javascript/the-case-of-the-disappearing-favicon/>

this is the code

```
function setFavicon() {
  var link = $('link[type="image/x-icon"]').remove().attr("href");
  $('<link href="'+ link +'" rel="shortcut icon" type="image/x-icon" />').appendTo('head');
}

```

Or (thanks to Mottie) using jQuery detach

```
$('link[type*=icon]').detach().appendTo('head');

```
I noticed this behaviour, too. Every now and then Firefox drops a favicon or it refuses to put the favicon alongside my bookmark. I think this is a Firefox bug.

To workaround this (and for other functionality), I installed the [Favicon Picker add-on](https://addons.mozilla.org/en-US/firefox/addon/7849). Of course, this doesn't solve your problem on other computers, like clients and the like.