Font Style Elements

These elements may be nested within one another. Browsers should, where practical, aim to combine different types of highlighting as required.
B (Boldface)
The <B> element specifies that the enclosed text should be displayed in a boldface. If this is not practical, an alternative mapping is allowed.
I (Italic)
The <I> element specifies that the enclosed text should be displayed, if practical, in an italic font (or slanted).
TT (TeleType)
The <TT> element specifies that the enclosed text should be displayed, if practical, in a fixed-pitch typewriter font.
U (Underline)
The <U> element specifies that the enclosed text should be displayed, if practical, as underlined. Not widely supported
S (Strike through)
The <S> element specifies that the enclosed text should be displayed with a horizontal line striking through the text. If this is not practical, an alternative mapping is allowed. New in 3.0.
BIG (Big print)
The <BIG> element specifies that the enclosed text should be displayed, if practical, using a big font (compared with the current font). New in 3.0.
SMALL (Small print)
The <SMALL> element specifies that the enclosed text should be displayed, if practical, using a small font (compared with normal text). New in 3.0.
SUB (Subscript)
The <SUB> element specifies that the enclosed text should be displayed as a subscript, and if practical, using a smaller font (compared with normal text). The ALIGN attribute for SUB is only meaningful within the MATH element. New in 3.0.
SUP (Superscript)
The <SUP> element specifies that the enclosed text should be displayed as a superscript, and if practical, using a smaller font (compared with normal text). The ALIGN attribute for SUP is only applicable within the MATH element. New in 3.0.

An example:

This text contains some <b><i>bold italic</i></b> text, some
<S>struck through</S> text and some <SMALL>small print</SMALL>.