As Victor has mentioned, MathJax only implements the math-specific macros of TeX, not the page layout features. For those, you need to use HTML or whatever markup language you are using to generate your web page. Victor's example looks like Markdown, but what you use will depend on the content-management system you are using (if any).
MathJax only handles what would normally appear between dollar signs, double-dollar signs, or in a math environment in a LaTeX document.
Davide