Google Chrome: Version 32.0.1700.107 m
This happens when displaying the profile and clicking on the number of visited days/consecutive.
The bug is in the AJAX response to the URL
Note the hardcoded
Simply removing the
Edit: Since this hasn't been properly fixed yet, I've included a client-side fix for this issue in Stack Overflow Unofficial Patch 1.8. Note that the fix won't prevent the "shield" icon from appearing when the calendar is first loaded, but it does reload the style sheet over HTTPS after the initial request over HTTP fails.