By default, DITA2Go generates <nobr> tags around non-breaking hyphens. However, the <nobr> tag is not included in the W3C DTD, despite the fact that all browsers support it. To eliminate <nobr> tags from the output, specify the following option:
[HTMLOptions] ; AllowNobr = Yes (default, use <nobr> tags around nonbreaking ; hyphens, supported properly by all browsers), ; or No (required for W3C validation) AllowNobr=No