Unless you need Arial's specific font characteristics in your stack, please just fall back to sans-serif. I hate these 'system font stacks' that don't fallback

Unless you need Arial's specific font characteristics in your stack, please just fall back to sans-serif. I hate these 'system font stacks' that don't fallback to my system because some schmuck thought it would be a good idea to put Ubuntu and Arial in these stacks instead of actually falling back to to the user agent or OS.