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 - Refresh the page by pressing ⌘R. The video show show the big red and white play button.
2 - Right Click on the video and select "Open Video in New Window" - this will open a new Safari page and will start playing the video in the new page displaying the native Safari control bar at the bottom of the video.
3 - You will see a subtitle icon in the control bar on the right. Click this and set subtitles to OFF.
4 - Close the new Safari window and return to the ScreenCastsOnline page. That should fix it!