(see guidelines for overcoming access barriers)
Use cascading style sheets to style your headings (using the H1, H2, H3, H4 tag) rather than using an image for a heading.
The marked up content can then be rendered differently according to user preferences. For example, screen readers index all <H> tags and allow users to browse by heading. If headings are in images then they would not be indexed.
Internet Explorer 6 on Windows will display MathML with the support of a plug-in called MathPlayer. Firefox and Netscape 7 and above will render MathML natively although extra fonts for some equations may be necessary - if so, the user will be prompted to download these. Always provide instructions for users if you use MathML in your design.
For more information on web accessible maths:
MathML provides the basis for including mathematical expressions in Web pages. Web developers in the past have often had to insert expressions as images in a html page to show format and even some operators. MathML can be used for both the visual presentation of mathematical notation and for expressing semantic content where scientific software and voice synthesisers are used.