I agree with the answer from Chris, but seeing this is a specific ASP.NET MVC question it would be better to use either Razor syntax:
<link rel="icon" href="https://stackoverflow.com/questions/487230/@Url.Content("~/content/favicon.ico")"/>
Or traditionally
<link rel="icon" href="https://stackoverflow.com/questions/487230/<%= Url.Content("~/content/favicon.ico") %>"/>
rather than
<link rel="icon" href="http://www.mydomain.com/content/favicon.ico"/>