.ico
, or is it just named ".ico"?The absolutely easiest way to have a favicon is to place an icon called "favicon.ico" in the root folder. That just works everywhere, no code needed at all.
If you must have it in a subdirectory, use:
<link rel="shortcut icon" href="/img/favicon.ico" />
Note the /
before img
to ensure it is anchored to the root folder.