Moodle - Browers Blocking "Mixed Content"
This article shows how to unblock and load contents from non-secure source in Chrome and Firefox for Moodle
There is a known issue in Firefox and Chrome that results in the display of a blank screen rather than loading the intended Moodle Content item when a user clicks a link.
Mozilla recently released Firefox Version 23, which seems to be causing some issues with loading certain content, especially noticeable within Moodle. Content within Moodle that is embedded and originating from a non-secure source, such as YouTube, is not displayed by default. This results in either a blank popup or an empty widget where the instructor or student expects there to be content.
Unblocking The Content In Chrome
A similar issue has existed within Chrome for a few months. The fix is similar. First, click the shield icon in the address bar at the right side then choose "Load unsafe script".
Unblocking The Content In Firefox
The fix is simple. Within the Firefox address bar, at the left side of the screen is a shield icon.
Clicking on the shield icon will drop down a menu labeled "Keep Blocking." Choose from this menu "Disable protection on this page". This should restore the content to the browser window.