OK, the first thing to note is that <i>
has been deprecated, and shouldn't be used<i>
has not been deprecated, but I still do not recommend using it—see the comments for details. This is because it goes entirely against keeping presentation in the presentation layer, which you've pointed out. Similarly, <span class="italic">
seems to break the mold too.
So now we have two real ways of doing things: <em>
and <span class="footnote">
. Remember that em
stands for emphasis. When you wish to apply emphasis to a word, phrase or sentence, stick it in <em>
tags regardless of whether you want italics or not. If you want to change the styling in some other way, use CSS: em { font-weight: bold; font-style: normal; }
. Of course, you can also apply a class to the <em>
tag: if you decide you want certain emphasised phrases to show up in red, give them a class and add it to the CSS:
Fancy some <em class="special">shiny</em> text?
em { font-weight: bold; font-style: normal; }
em.special { color: red; }
If you're applying italics for some other reason, go with the other method and give the section a class. That way, you can change its styling whenever you want without adjusting the HTML. In your example, footnotes should not be emphasised—in fact, they should be de-emphasised, as the point of a footnote is to show unimportant but interesting or useful information. In this case, you're much better off applying a class to the footnote and making it look like one in the presentation layer—the CSS.