Proving the validity and accessibility of dynamic web pages

If a static web-page is checked for accessibility and passes then all is well. However checking the accessibility of the output from a dynamic (scripted) web-page is like testing a program to find errors. However many times a test succeeds it is always possible that the program will produce bad output next time. What is needed is something closer to a proof of correctness. This paper describes a first attempt to provide a proof of validity for dynamic web-pages which can be extended to a proof of accessibility.