Here is Chrome's explanation and a way to turn it off and as mgnade said, it is browser specific Waterfox views them just fine:
Although not recommended, you can also use the command line flag --allow-running-insecure-content to prevent Chrome from checking for insecure content. Instructions on how to add a command line flag can be found on our Chromium site
. Issues may sometimes stem from poorly-made extensions or insecure CSS/Flash.