It says "Leave url blank to submit a question for discussion", I guess it is "space" button on keyboard, but it didn't work. It says "please enter url". I event tried to copy and paste "blank" symbol.
you mean Ask HN? Those are normal posts like the one you just did. Just literally type Ask HN: (question) as the title, leave the URL blank and you're good
00h this is what I mean, thanks
Blank means don't put anything there. Not even a space.