Can mix and match (boldtalics, boldlining, undertalics, boldtalicslining, in normal and courier both).
Donít overlap tags, but nest them: GOOD: <B><I> ÷ </I></B> BAD: <B><I> ÷ </B></I>Browsers might do the right thing, but weblint and other HTML sanity checkers will yell at you fiercely.