Is the following valid HTML?
As an HTML element I can\'t see why it wouldn\'t be, but I don\'t think I\'ve eve
Yes, is valid.
Specification tells that br accepts global and event attributes, and class is a global one.
Note that if you target HTML4 and below, there's an specific attribute for br named clear, which defines where to put the new line, as stated here, but now is deprecated and unless your DOCTYPE lets you, you should not use it anymore.