> I could see formal methods proving that only valid HTML was ever emitted. I think we could also prove the absence of XSS vulnerabilities. That would be very

> I could see formal methods proving that only valid HTML was ever emitted. I think we could also prove the absence of XSS vulnerabilities. That would be very valuable. > But how do you prove that your layout aligns on Firefox 55.0.3? This is harder, admittely. Mozilla is probably not going to provide the formal model that haskellandchill imagines, unless that model can be automatically extracted from the actual code, which may be possible someday.