> cat file.tr | nroff -mms | groff -Thtml I'm not sure what you're trying to accomplish. I don't think it makes sense to process already-formatted text (from the nroff run) with groff again. It's also unclear whether your error messages are from the "nroff" or the "groff -Thtml" process. (Btw, "nroff" is basically "groff -Tascii" or "groff -Tlatin1" or "groff -Tutf8".)
You could try groff -ms -Thtml file.tr >file.html Also, you have several lines beginning with an apostrophe. The apostrophe is by default the no-break control character, so groff complains about an undefined macro it thinks you're trying to call. You should substitute apostrophes which are meant to be left quotes by "`" (character code 96 in ASCII) or "\[oq]" (or "\[lq]" if you want double quotes).
