I did some edits on the original css files but it was before updating. I did not know about the 'all edits must go to EXTRA.css' before doing so.
I just did this. The error on the index page is gone. But I don't seem to have my user info showing up?It's not a big deal, but yes typically EXTRA.CSS is meant for all your edits. We change xb.css / xb_style.css almost every update so ideally that shouldn't be edited at all. What I'd do it simply copy your xb_style.css on your child style.
Paste it in a program like notepad++ (free), revert your template. Then re-apply your CSS into extra.css