[increase]

I was using the sigil files to edit the chapters, the error messages were given as to font

ie
ERROR OEBPS/Text/chapter1.htm 75 59 Error while parsing file: element "font" not allowed here; expected the element end-tag, text or element "a", "abbr", "area", "audio", "b", "bdi", "bdo", "br", "button", "canvas", "cite", "code", "command", "datalist", "del", "dfn", "em", "embed", "epub:switch", "i", "iframe", "img", "input", "ins", "kbd", "keygen", "label", "link", "map", "mark", "meta", "meter", "ns1:math", "ns2:svg", "object", "output", "progress", "q", "ruby", "s", "samp", "script", "select", "small", "span", "strong", "sub", "sup", "textarea", "time", "u", "var", "video" or "wbr" (with xmlns:ns1="http://www.w3.org/1998/Math/MathML" xmlns:ns2="http://www.w3.org/2000/svg")

But I also edited the content.opf and toc.ncx