HTML and CSS Reference
4.4.16. Allowed Usage
Any content-based style tag may be used anywhere an item allowed in
text is used. In practice, this means you can use the <em> , <code> , and
other similar tags anywhere in your document except inside <title> ,
<listing> , and <xmp> tagged segments. You can use text style tags in
headings, too, but their effects may be overridden by the effects of the
heading tags themselves.
4.4.17. Combining Content-Based Styles
It may have occurred to you to combine two or more of the various
content-based styles to create interesting and perhaps even useful hy-
brids. Thus, an emphatic citation might be achieved with:
In practice, Dr. Frankenstein, the browser usually ignores the monsteras
you can test by typing and viewing the example yourself, "Moby Dick"
gets the citation without emphasis.
The HTML and XHTML standards do not require the browser to support
every possible combination of content-based styles and do not define
how the browser should handle such combinations. Someday maybe;
for now, it's best to choose one tag.