I'm sure this question is asked by a lot of requiters, but here's my answer. CSS3 was released back in 1999, so what is the point of even asking about something which was obsolete so long back. Given the fact, you mention the requirements of 1 Year experience in CSS, how would you expect someone of such experience remember something which was changed so long ago? Even if someone answers it, surely it's because either they know about your scripted questions from google or somewhere, or they have been asked by the same questions by other interviewers like you. Also, I was told your company itself was started in 2011, so you yourself don't use old CSS, then why bothering even asking such a question? Infact, CSS3 is now supported in each and every modern browser and even older ones back from 2010. So I am led believe this is just a script some of the requiters are following, maybe from some website searched on google like "top interview questions on CSS" or so. My suggestions: 1) Ask questions that matches the requirement of your Job. 2) CSS3 (a.k.a CSS level 3) is in fact an extension of CSS1, so it already includes all the features of CSS, so if you really want to test my knowledge about CSS, ask me questions about the features of CSS3 or give me some sort of a test. Please don't get me wrong, I am not here to criticize, but I really want to know the reason why these kind of questions are asked.