I have a favicon on my site but don't do anything other than place the favicon.ico in the portal root. Checking my page source I see I have a favicon link so I'm guessing the DNN is putting the link in for me. I'm using 4.8.2. Check to see if the link automatically appears for you once you have the favicon in the right place. If not, which version of DNN are you using.

Cheers, Rhys

That' correct.  FireFox does the same thing.  They hold on to the Favicon entirely too long.  I am not sure where it is stored either, because I have cleared out cache files in both browsers in the past, and it seems to be hit and miss as to when the new favicon will appear, but over time it always does.

A little side note though...  If you happen to have more than one portal on that single DNN installation, you can put your favicon in your root portal folder and DNN will pick it up for each site.  For example:

~/Portals/0/favicon1.ico
~/Portals/1/favicon2.ico

Just a tip that I hope helps you (or someone else).