There are three main styles for coding mathematics for HTML display:
TeX/LaTeX
\[ f(x|\mu,\sigma^2) = \frac{1}{\sqrt{2\pi\sigma^2}}e^{-\frac{(x-\mu)^2}{2\sigma^2}} \]
AsciiMath
` f(x|mu,sigma^2)= 1/sqrt(2 pi sigma^2) e^(-(x-mu)^2/(2sigma^2)) `
MathML