This is the official manual for the latest Org-mode release.
Plain ‘<’ and ‘>’ are always transformed to ‘<’ and ‘>’ in HTML export. If you want to include raw HTML code, which should only appear in HTML export, mark it with ‘@@html:’ as in ‘@@html:<b>@@bold text@@html:</b>@@’. For more extensive HTML that should be copied verbatim to the exported file use either
#+HTML: Literal HTML code for export
#+BEGIN_EXPORT html All lines between these markers are exported literally #+END_EXPORT