How to throw invalid arguments

1

Any time I throw invalid arguments my codes does not behave the way I want it it returns something like
“What. () width
What is wrong with my code

2

Hi,
1st welcome in here.
Before anyone would answer what would be wrong with your code,
can you tell what is wrong with your question?

This is what I see

image
image809×308 15.9 KB

Best Regards.

EDIT:
Here are a few hints from other new questions

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