HTML5 Security
Security measures introduced in HTML5 can facilitate secure use of CDNs and social plugins.
HTTP Security
HTTP headers can be used to harden web app security. Headers could also be leaking information about web app internals.
Google Safe Browsing™
Google's Safe Browsing™ repository contains a list unsafe web resources. Check URLs against the Safe Browsing service.
Connection Security
Perform basic health checks about various issues related to Transport Layer Security (TLS).