Remember when Mark Zuckerberg blamed the problematic old Facebook mobile app--dubbed "freakishly slow" by some--on "betting too much on HTML 5?" So does backend-as-a-service (BAAS) provider Sencha, and to rebut Zuckerberg's assertion that using HTML5 was "one of [Facebook's] biggest mistakes," Sencha built its own mobile webapp, Fastbook, to demonstrate that HTML5 is ready for prime time.
When the time comes to test how various implementations of different types of browsers actually work with a particular application, much trial and error still exist. Despite the rise of application testing services in the cloud, testing browser compatibility against a production application is still problematic. More often than not, when testing does occur, it’s against a replica of the application running in a different environment, being accessed by browsers that might not even have any of the plug-ins that the application may need to support in a production environment.