I noticed a new bug in TIpHtmlPanel. When you have comment-tags in css-part of html-file this css-part is ignored:
<style type="text/css">
<!--
This part is ignored due the tag-comment.
body{ font-size:9pt; font-family:Arial, Helvetica, sans-serif }
table{ font-size:9pt; font-family:Arial, Helvetica, sans-serif }
-->
</style>
It is worked in lazarus 1.8.5.