It depends partly on exactly what you are attempting and how automated it
needs to be. If you are inserting INCLUDETEXT fields, make sure you use the
\c HTML switch. But Word may have difficulty includetexting more complex
pages, in which case you would probably be better off opening the HTML file
in Word and saving it as a .doc before including it. If the HTML file won't
open properly using Word File|Open, then either it has some feature that
Word does not recognise or there could be something wrong with it. The same
is true of RTF files - if they were generated by Word, they should be OK.
You also need to be careful that different files do not use the same style
names in different ways, because in the composite Word document, a paragraph
or character style can only have one definition.