Making OPA interviews compliant with the Americans with Disabilities Act

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I have an OPA  interview called from Service Cloud that I need to make compatible with the Americans with Disabilities Act.
Here are three examples of what I need to do to make the interviews more accessible for sight impaired people. I have no idea how to access the HTML inside the interview to fix these things:

1. I need  to ensure that error messages are explicitly indicated when the user clicks the next button on an interview screen.
Currently  when a user does not enter a value for a required field, the error message "This value is mandatory" does not receive focus.  As a result, as creen reader user is unaware of the problem area(s)  on the page.