Hello,
Consider the document has this style ( present in styles.xml ):
<w:style w:type="character" w:styleId="CustomEmphasis">
<w:name w:val="Custom Emphasis"/>
<w:basedOn w:val="DefaultParagraphFon…...When this docx is converted to html, the span class uses the Id...definitions like so, <w:style w:type="table" w:default="1" w:styleId="TableNormal">...