I ran into Error Message 404.8 following along in chapter 1 the first time I tried to view in my browser the first page I had created with webmatrix. I couldnt find anything in the book about it and I couldnt find a thread here yesterday with a fix. I figured I would save the next person the hassle of tracking a solution down.
The error message description was "The request filtering module is configured to deny a path in the url that contains a hiddensegment section". My requested url was http://localhost:333963/App_Data/page.cshtml
I found the general solution here:
This is what I did to correct mine on both my desktop and laptop:
1. Clicked start and searched for applicationhost.config
2. Right click on applicationhost.config and select properties to find and copy path.
3. Click Start, type Notepad in the Start Search box, right-click Notepad, and then click Run as administrator.
4. On the File menu, click Open, and paste the path and click open (make sure you are viewing all files not just .txt)
5. Select and open ApplicationHost.config
6. In the ApplicationHost.config file search (crtl-F) for "hidden" or "hiddensegments" which will locate the <hiddenSegments> element.
7. Microsoft says in the <hiddenSegments> element, you can either delete the entry that matches the directory that is specified in the requested URL.
Instead of deleting code I edited the line to read:
<!-- add segment="App_Data" / -->
8. On the File menu, click Save.
9. Exit Notepad.
Hope that helps someone.