У вашего броузера проблема в совместимости с HTML5
solve brightness problem windows 10 for lenovo z500
Reference : http://answers.microsoft.com/en-us/windows/forum/windows_10-other_settings/lenovo-z500-touch-brightness-not-working-after/2773793e-c609-44c6-a75a-6ba8c31c3909?auth=1