im not trying to develop a tool that valid but to make a website looks better

thanks

I am wondering why using sans here will make a website looks better since sans is not valid generic font family and the browser will simply ignore this value. If so, sans should be deleted.

not because of sans or sans-serif but the whole lib,
pull-request that makes a website looks better will be merged but not one that makes valid

After browsing on the history I found that sans-serif was replaced by sans in 5c96950, could you explain why sans-serif should be replaced by sans here? Is it related to any WebKit bugs? Thank you.

after a review, i think you are right on this
thanks, again

You are very welcome.