depends, if you want a consistent font across a website it's hard with free fonts, because these usually come in bold/regular/italic and that's it, professional font will come with all combinations with wide and narrow lettering on top, plus light and black, so it will cover everything from titles to footers, with a good coverage of unicode glyphs on top of it.
the free ones that come close, like the dejavu font family, are very few and overused.
There is one reply to the same comment as yours with a free font that looks pretty much like this one that has about 3 times as many styles as it. And all of them look fine.
the free ones that come close, like the dejavu font family, are very few and overused.