michal_h21It is not placed in tex4ht.sty or in latex.4ht, but it is in cond4ht.4ht, which is included in the output formats.
michal_h21I've fixed one issue that was quite mysterious to me: that all monospaced fonts were smaller than surrounding text. Now I found an answer: http://code.iamkate.com/html-and-css/fixing-browsers-broken-monospace-font-handling/
michal_h21So I've updated the htf files and configurations for HTML. The updates should be in TL soon, hopefully.