To increase fonts in tex4ht
if using 12 pt in document class, add this line after the \document section in the .cfg
file
\DeclareMathSizes{12}{14}{10}{8} \DeclareMathSizes{12}{16}{12}{10} %----> for {\Large}
(note, \Large in a 12pt article is 17.28pt
The size of math’s font changes also with \Large
To make Math look better, see this
http://tex.stackexchange.com/questions/43772/latex-xhtml-with-tex4ht-bad-quality-images-of-equations