HTML to DOc conversion.... CSS not being imported

I am trying to import a html doc that has CSS formatting, however the CSS isnt taking effect?

is there a special way that i need to include the CSS?

e.g. does all css have to be inline? can i use classes and unique id’s?

where on this site can i find the information on importing features rules etc.

External CSS is not supported yet, as well as use of classes and ids. Only inline styles are supported. Supported export/import feature list for PDF and HTML can be found here:
https://docs.aspose.com/words/net/features/

Hope this helps. Please let me know if you have further questions.