Is it OK to use unknown HTML tags?

Question

Correct me if I\'m mistaken, but AFAIK, unknown HTML tags in markup (i.e. tags not defined in the HTML spec, like say, ) will eventually be treate

Answer 1

No. You will fail validation, you will get random issues cross browser and you WILL be eaten by said dinosaurs. CSS is the answer if you want your page to behave predictably.