Family Historian only allows an export of a tree as a picture (JPG or PNG or BMP, etc). I think that it may be quite difficult to export it as html. But I am willing to be proved wrong.
Inserting it as a picture on a webpage may be the way ahead. IN my experiment a png file wasn't too big and the download time wasn't too long.
Family Historian does an ancestor outline report which can exported as html but it loses the lines.