"Oh gods, what have you done?!"
You hear Sam cry out as you input your own custom CSS code.
You had no way of knowing the software wouldn't be compatible.
Not only is your code incompatible, but it's also corrupted the existing script. It's now caught in a feedback loop as it tries to reconcile the error, only corrupting itself even further.
The pub's patrons dissolve into strings of unknowable code. The tavern itself degrades into a backdrop of meaningless static. A pop-up which reads "Reality.exe has stopped working. Please restart," hovers in front of your vision.
It may have only been a fiction, but nonetheless your actions have destroyed this world.
So I hope you're proud of yourself.
You can rollback to an earlier point, a back-up pre cock-up.
And try to get it right this time.