Troubeshooting IIS

Client errors : 4xx
Server errors : 5xx

see https://support.microsoft.com/en-us/kb/943891

Analyzing Crash Dumps
https://msdn.microsoft.com/en-us/library/windows/desktop/ee416349%28v=vs.85%29.aspx

Debug Diagnosis
https://www.microsoft.com/en-us/download/details.aspx?id=40336

Logging Frameworks
http://www.dotnetlogging.com/
https://logging.apache.org/log4net/

Resources
http://windowsitpro.com/web-development/iis-troubleshooting-tips-and-tricks
http://programmers.stackexchange.com/questions/57064/best-practices-for-logging-and-tracing-in-net