Letters or numbers that are raised or lowered slightly relative to the main body text are called superscripts and subscripts, respectively. (X)HTML includes tags for defining both kinds of offset text.
To create superscripts or subscripts:
Figure 4.15. The opening sup or sub tag precedes the text to be affected.
Figure 4.16. Unfortunately, the sub and sup elements spoil the line spacing. Notice that there is more space between lines 6 and 7 of the first paragraph and lines 4 and 5 of the second than between the other lines.