Sometimes when I navigate to a page in Stack Overflow, Internet Explorer will warn that "Only secure content is displayed." The only HTTPS requests logged in Developer Tools are to
- www.gravatar.com (image/png)
- a248.e.akamai.net (image/jpeg)
- view.atdmt.com (text/html, frame navigate)
For example, the warning appeared when the ad below was shown. The ad is located within an
<iframe src="https://view.atdmt.com/..."> within an
<iframe id="ados_frame_adzerk..."> within a
<div class="everyonelovesstackoverflow adzerk-vote" id="adzerk...">.