<!-- <o:tag>Coulomb's law</o:tag> -->
replace ' by chr 146
Tidy outputs the same as above but replaces the chr
(146) by chr(25) for whatever reason. Since comments
do not allow character references, characters in
comments must be representable in the character
encoding. If the character encoding is e.g. US-ASCII or
ISO-8859-1 the mentioned character cannot be output.
What to do in this case? Fail completly? Replace the
character by '?'? Remove the character? Change the
output encoding to UTF-8?