Quote:
Originally Posted by roger64
Contrary to nbsp, nnbsp do have a fixed width (with variable interpretations  ). |
This is not defined anywhere and is subject to change based on what a browser (or word processor, etc) implementation thinks is most aesthetic. Many browsers used to use an unadjusted width for nbsp, but that's changed in recent years because it looks horrible in many common cases. You also noted that Word has gone back and forth on that question. nnbsp could likewise act differently in different programs.
If I wanted a guaranteed fixed width space that didn't break, I'd use one of the defined fixed width spaces (en space, 3-per-em space, etc) inside a span or other element with a "white-space: nowrap" style attached.