THEY SHOULD HAVE CALLED IT MOZILLA HOTBIRD
Half the people who use Firefox use it to look at porn!
Favicons are stupid and so is Firefox. Let me explain. Favicons, short for "favourite icons" or something, was a concept invented by Microsoft, for Internet Explorer. Recall that IE calls bookmarks "favourites" so they're icons for favourites. There's some ghoulish spiel about using them to "increase the identity of your website" but basically it means you get your own icon next to your site in somebody's bookmarks file. That's the point. Of course with the advent of tabbed browsing the dratted things creep into your tabs as well.
There's two ways of implementing favicons, let's call them "per-site" and "per-page"
- per-site favicons are implemented in a horribly non-standard way by IE (and coerced by Firefox); you put a file called "favicon.ico" in your documentroot and it loads that
- per-page favicons are slightly more tolerable, you put <link rel="shortcut icon" type="mime/type" href="path/to/icon"> in your page header. The jury is still out on whether it's "shortcut icon" or just "icon"; some say the rel string is a space separated list rather than a single string. I don't know.
Anyway the point of all this is that Firefox in its infinite wisdom implements favicons in such a way that if your site, say with URL "http://myhost.com/mysite/" provide neither of these two methods it will with EVERY SINGLE FUCKING PAGE REQUEST generate a SECOND request for "http://myhost.com/favicon.ico". This is fucking bullshit and it needs to stop.
Therefore I would ask anyone reading this to type "about:config" into their address bar (or copy and paste that link, you don't seem to be able to click on it, probably for security reasons) and set browser.chrome.favicons to false.