I've seen some 'mistakes' written so many times around the internet, I was wondering if they were really mistakes or if I was wrong. Would things like these be appropriate for formal use?

What University do you go to?

The correct way to write that would be, "Which University do you attend?", right? I've seen "what" used in the place of "which" so many times, I was wondering if that is actually considered correct.

Is that sarcastic?

I assumed that "ic" should be replaced by "ism", is this correct?

While not appropriate for very formal use, these are correct and widely used.

"what" in place of "which" is extremely common because the two are so similar in meaning.

"go to" for "attend" is just a more colloquial expression -- also extremely common.

"ic" is correct in "Is that sarcastic?", as is "sarcasm".

That is sarcastic = That is a sarcastic remark.

Emotion: geeked
1-- Head of the Department if that is his title; the head of the department if that is his function.

2-- Either is fine. Authorization as a perquisite is uncountable; authorization as an individual action, spoken or written, is countable.
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Which is correct:

He is the Head of the Department or he is Head of the Department.

He will do it only when he receives formal authorization from you or he will do it only when he receives a formal authorization from you.
 Mister Micawber's reply was promoted to an answer.
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