[30minAdayHN]

back in 90s on windows, our secret directory used to be alt+255 (it looks like a space but not space i think)

[lifthrasiir]

Which is a non-breaking space (U+00A0), which is mapped to 0xFF in the code page 437. (You need to put a leading zero to access to Unicode code points, like alt+0255 for U+00FF ÿ.)

[brunorsini]

I did the same thing. One more of those habits that didn't survive the transition to Mac OS X.