In order to use MathML successfully, one may use one of the following most common software configurations:

• Firefox 1.9 or higher with fonts installed. The installation process is described at
  Mozilla site
• Internet Explorer with MathPlayer, which must be downloaded and installed.
  This is the download site.

In order to use the JavaScript software LaTeXMathML one must include or link a JavaScript source file from this site.

If your browser is set up correctly, the following formula should show correctly:
$x^2$
And so would this, which should be a displayed equation:
$\displaystyle{\int_{-\infty}^\infty e^{-\frac{t^2}{2}}\,dt=\sqrt{2\pi}.$