Plain ‘<’ and ‘>’ are always transformed to ‘<’ and ‘>’ in HTML export. If you want to include simple HTML tags which should be interpreted as such, mark them with ‘@’ as in ‘@<b>bold text@</b>’. Note that this really works only for simple tags. For more extensive HTML that should be copied verbatim to the exported file use either
#+HTML: Literal HTML code for export
#+BEGIN_HTML
All lines between these markers are exported literally
#+END_HTML