All is needed is to have editor that can show white spaces (i.e. show tabs differently than spaces, after all those are two different characters).
With that the whole issue with tabs and spaces no longer exists.
BTW if you are copying snippets of code from website "as is" in any language you will have to reformat it to fit your structure. Also if you copy code so often that this is becoming an issue I'm not sure I would want someone like that working for me.
And this happens all the time to professional developers, much less 9-year-old beginners.