Symptoms
Errors: HostServer]"System.Exception: Form 'favicon.ico' could not be found, or is not checked in." Browser Console]"GET https://domain/favicon.ico 401 (Unauthorized)"
Diagnoses
Custom favicon was not fully configured.
Resolution
Step 1: Add the favicon.ico to the location that your K2 IIS sites are point to. (Ex. C:inetpubSmartForms, C:inetpubK2 blackpearl)
Step 2: Temporarily Enable the authentication on the K2 or SmartForm site for Forms Authentication and Anonymous Authentication.
Step 3: Restart the K2 service and do an iisreset. Test the forms and the favicon error should be gone.
Step 4: Disable the authentication that you enabled in Step 2 and restart the K2 service again and do an iisreset.
Some alternative solutions are detailed on K2 Community: http://community.k2.com/t5/K2-blackpearl/Favicon-in-K2-SmartForms/td-p/82902
