Answer 1

on the website of the author of c++ it's said in the FAQ that void main is not c++. So the best is to avoid it, even if some compilers allow that, it is not standard...
A program should return 0 when everything gas been done with success and an other int value to refer an error code when something got wrong.

source : http://www.stroustrup.com/bs_faq2.html#void-main