How to present mathematical expressions using a language that has so little markup for them? Sometimes you can use MathML, but often you need to resort to images.
Useful tools and tricks article mentions a nice on-line LaTeX equation writing tool at CodeCogs.com: You type in LaTex or MathML and it creates an image of the formula. You can then take that image and put it on your website.
You can go find most any equation in Wikipeda, then hit the “Edit” link to see the LaTex MathML type text expression. Just cut-and-paste that into the CodeCogs window and it will create the formula as an image. So code int_a^b ! f(x),dx , becomes this: