That lack of understanding also includes unwarranted use of FP when a simpler representation like fixed-point or BCD (or even integers) would work for the application, without introducing all the subtleties of FP math. Of course, this advice doesn't work in a language like JS where all numbers are FP, so in that case understanding them is the only choice.

One of the instantly recognisable symptoms of float-abuse is NaNs appearing in odd places:

https://what.thedailywtf.com/t/i-dont-look-forward-to-having...

http://i.imgur.com/viPztah.jpg