This works:
<!doctype this is junk >
OMIGOD my next page will absolutely have
<!doctype w00t>
if that really does work down to IE5 and FF2!
Making a typo in these will not always default to quirks mode but only when the typo nullifies one part and then the remaining part matches the requirements for quirks mode.
…this won’t [work]:
<!DOCTYPE HTML PUBLIC what is this for “-//W3Cxxx/DTD rubbish HTML 4.01//EN” “Nonsense here http://www.w3.org/TxxxR/html4/strict.dtd”>
Hm, that makes sense: my double space was somewhere around the “EN” part, which would break the “4.01//EN” section.