I don't think any Html question is "horribly erroneous" though😂
We've been practicing them for quite a while now.
Still as Michal Straka said, you can use the in-app report feature to report wrong questions/answers.
You can report wrong answers or wrong questions. Click 'VIEW CORRECT ANSWERS' after finishing a challenge. Then there is always a small icon on the right at the top. Click it and you can report different types of errors:
Keep in mind to test the answer before reporting it. The results can be sometimes surprising.