If when playing videos on your Mac, you may see two sets of subtitles being displayed, but if you try to switch off subtitles using the video player controls, one set remains.
This is usually due to Safari trying to display subtitles as well as the ScreenCastsOnline video player. In order to switch Safari subtitles off, follow these instructions:
1 - Click on the Download button on the video page and click on one of the videos. This will start it playing in a separate Safari window.
2 - You will see a subtitle icon in the control bar on the right. Click this and switch off subtitles.
3 - Then switch off the control bar by Ctrl or right clicking on the video and select Hide Controls. That should fix it!