The AssistiveMML.js extension

The options below control the operation of the AssistiveMML extension that is run when you include "AssistiveMML.js" in the extensions array of your configuration. They are listed with their default values. To set any of these options, include a AssistiveMML section in your MathJax.Hub.Config() call.

For example

MathJax.Hub.Config({
  "AssistiveMML": {
    disabled: false,
    styles: {
      ".MJX_Assistive_MathML": {
        position:"absolute!important",
        clip: (HUB.Browser.isMSIE && (document.documentMode||0) < 8 ?
               "rect(1px 1px 1px 1px)" : "rect(1px, 1px, 1px, 1px)"),
        padding: "1px 0 0 0!important",
        border: "0!important",
        height: "1px!important",
        width: "1px!important",
        overflow: "hidden!important",
        display:"block!important"
      }
    }
  }
})

would enable the extension and defines CSS Style Objects to define CSS applied to the MathML content embedded in the page.