ODT is supported by 
MICROSOFT WORD 2007 + 


It's and OPEN standard. 
( I support open standards )
It's 40% smaller in most cases.

To use ODT when you can't open it is simple:
- UPDATE YOUR MS WORD -
or download  LibreOffice / Openoffice 
or use google docs without installing ANYTHING 
All can handle the file. 

HTML as backup is included because it keeps things NEAT > Instead of jumbled -Beyond repair.-
DO NOT ASK FOR A TXT VERSIOn, -it's unreadable. -