Why loading third party scripts async is not good enough:
Loading third party scripts async is key for having high performance web pages, but those scripts still block onload. Take the time to analyze your web performance data and understand if and how those not-so-important content/widgets/ads/tracking codes impact page load times. Maybe you should do what we did on CDN Planet: defer their loading until after onload.
All of us have a lurking failure in our websites: 3rd party scripts from ads, widgets, and analytics. How is it that one script can bring down your website?