Http Module not loading in IIS

For the project i am working on we created an Authorization component which loads as Http Module and works on the user credentials.
The module was defined in web.config for the web application and was working fine. Until one day i tried to play with App pool settings of IIS and then the module just stopped loading.
After doing some searches on web i finally figured out the problem. While playing with the App pool settings i had changed it to run in Integrated mode from the Classic mode.
When i run my application pool in the Integrated mode the module has to be specified in web.config as an entry under system.webserver tag while if i am using the classic mode the http module has to be specified under system.web tag of web.config.

How this matters and what these 2 modes mean is something i still have to figure out but for now i am happy that my module is up and running for me to go ahead and work on my tasks :)

Happy coding

~Abhishek

HTTP Error 503. The service is unavailable.

Another one of those errors which drives a developer crazy.
One of the reasons it could be occurring is because your site is running under an AppPool which is unable to start because of reasons like wrong identity etc.
The problem is that it is very difficult to catch this since the site seems to be up and running in IIS 7 management console.
Once you reach the place where all the App Pools would be listed you might see that the App Pool is not yet started and hence the problem. There's no way that the Management Console would give you a hint as to what might be going on. At least on the Console it looks like everything is up and running fine.
So next time you see a Http Error 503 you can go and check the App Pool settings before doing anything else.
@IIS Console team :-It should be easy to figure this one out and display an error to administrator saying something is wrong with App Pool settings.

Happy coding...

~Abhishek