Why does a browser send two requests for the same page when it's refreshed?

I think it's to do with this bug in Chrome where it's sending a request for the favicon on every request. Firefox and other browsers do this on their first request but cache it.

As found in another answer, it can be caused by empty src attributes on images or iframes. I had the same problem : 4 requests on the exact same page — not on the favicon — from Chromium, when doing only 1 page refresh. In my case, I found out it was due to empty href attributes on link tags :

<link rel="shortcut icon" href="" />
<link rel="icon" type="image/x-icon" href="" />
<link rel="icon" type="image/png" href="" />

So 1 request for my page reload, and 1 request for each of the 3 above links.