Matt's devblog

I probably come across this error at least once per year. Ran into it again today when setting up a website to host locally in IIS, on a computer I don't use much.

HTTP Error 500.19 - Internal Server Error
The requested page cannot be accessed because the related configuration data for the page is invalid.

Detailed Error Information:
Module   IIS Web Core
Notification   Unknown
Handler   Not yet determined
Error Code   0x8007000d

Config Source:
   -1:
    0:


Microsoft's documentation for that error code helpfully points out:

"This problem occurs because the ApplicationHost.config file or the Web.config file contains a malformed XML element."

Well that clears it up. Just remove the malformed XML element on line 0...

Except that the site runs just fine on other systems, and even in IIS Express on the same machine that's causing the error, so clearly there's no "malformed XML".  Anyway, it turns out that if your web.config has a section for something li…

If you find that the "Formats" list in an Umbraco RTE refuses to open, and the Javascript console contains this error:

"Cannot read property 'parentsRequired' of undefined"

Check the stylesheet that the RTE is using.  In my case, adding this style had triggered the issue:

/**umb_name:Small*/
small{}

Although there's nothing wrong with this style itself, the problem is in what TinyMCE considers to be "valid" HTML elements.  Why is "small" not valid?  No idea!  But you can fix this by opening /config/tinyMceConfig.cfg, finding the <validElements> section and appending this:
,small[class]
And that's it!  You can probably substitute "[class]" with other attributes if you need to, or even just [*].  I'm not really sure what all the implications of that are (let me know if you find out), so I just went with [class] like some of the other properties have.

Credit to Eric Schrepel for helping me figure this one out at h…