Firefox 23 features improved security for webpages with mixed http and https modes

https://blog.mozilla.org/security/2013/05/16/mixed-content-blocking-in-firefox-aurora/

QUOTE: Firefox 23 moved from Nightly to Aurora this week, bundled with a new browser security feature. The Mixed Content Blocker is enabled by default in Firefox 23 and protects our users from man-in-the-middle attacks and eavesdroppers on HTTPS pages. When an HTTPS page contains HTTP resources, the HTTP resources are called Mixed Content. With the latest Aurora, Firefox will block certain types of Mixed Content by default, providing a per-page option for users to “Disable Protection” and override the blocking.