If you previously designed your web site using global.asa file (for some object initialization) you may wonder why site does not properly work.
To solve this issue, just configure the path where the global.asa file resides as an application.
If path was already configured as a virtual directory, you can simply right click on the right virtual directory and choose 'Convert To Application'
http://www.w3schools.com/asp/asp_globalasa.asp
http://stackoverflow.com/questions/7255685/reading-web-config-values-in-classic-asp
http://www.iis.net/learn/application-frameworks/running-classic-asp-applications-on-iis-7-and-iis-8/classic-asp-not-installed-by-default-on-iis