I'm trying to find a shim which will stop Firefox 3.5 - 3.6 (under Prism) to stop submitting a form when the input is set to required
.
I've just tried using Afarkas's webshim but that hasn't worked either.
Try out the Web Forms polyfills on the Modernizr list.
https://github.com/Modernizr/Modernizr/wiki/HTML5-Cross-Browser-Polyfills
This one appears to do the trick: http://ericleads.com/h5validate/