The Enthought Training on Demand web application shows green "play buttons" and blue lock icons to indicate whether a given lecture or exercise is accessible for users without a full subscription. These icons are provided using a special font set. However, on Internet Explorer 10 and 11, the Windows Internet security options can be set such that font downloads are blocked. In this case, these icons will not appear.
You can check the security settings by going to the "gear" icon in Internet Explorer (or prettying Alt-T) and selecting "Internet Options". A tabbed dialog will appear, select the "Security" tab. Press the "Custom level" button, which brings up a large list of security options. About midway down is a heading called "Downloads", the second option of which is "Font download". This option needs to be enabled in order for the icons to appear.