In computing, quirks mode refers to a technique used by some web browsers for the sake of maintaining backward compatibility with web pages designed for old web browsers instead of strictly complying with W3C and IETF standards in standards mode.
https://developer.mozilla.org/en-US/docs/Web/HTML/Quirks_Mode_and_Standards_Mode
https://developer.mozilla.org/en-US/docs/Mozilla/Mozilla_quirks_mode_behavior
JavaScript