Expand allowed HTML tags
Book element
The Allowed HTML tags made available to content authors by default in the Limit allowed HTML tags input filter used in the default Filtered HTML text format is a bit too limited. For example, if we want to let people add images, headlines, or superscript text, we need to add the tags that make these possible: img, h1 through h6, and sup.
Here is an example of an expanded allowed tags list