(NOTE: I'm not writing this blog entry for my "audience"; I'm writing it to help me remember this issue a year from now. I do that sometimes. Don't worry, you'll get used to it.)
So the other day, someone shows me a specific Filemaker database being served up via Instant Web Publishing (aka IWP). They ask me to help them make a modification on the webpage that people land on when they logout/exit the application. No problem, I figure-- it's obviously a static page because it already contains customized content on it. All I have to do is drill down into the IIS webroot subfolder, locate the page, open it up in Notepad and make the requested changes.
Naturally, the customized database homepage could not be found in the webroot folder. I searched for it manually, I asked Windows to search the folder and subfolders based on strings of text we could see in the page via the browser. Nothing, nada, zip.
It turns out that when you customize the default database homepage for Instant Web Publishing, you do so by creating a file called iwp_home.html. However, you don't put this file in the webroot folder of your web server. This file resides inside a subfolder of the actual Filemaker folder itself, which is completely outside the webserver's normal document path. It's basically the lone exception to the "all static pages can be found in the wwwroot folder" rule.
Fool me once, shame on you. Fool me twice, shame on me. ;)