Mixing MathML with other markup

A fraction with the animated throbber as denominator... View the source...

\frac{a}{}

Fill the gaps in this matrix with input fields

[\begin{matrix} a \\ d \end{matrix}]

See the difference of rendering between

{jif}^{jif}

-- italic MathML <msup> and
jif^jif -- italic HTML <sup>

And there could be more...

Mixing MathML markups and other markups to get special effects