It is irritating to many people when they click on a web page to read it and a video on the page starts playing with noise coming out the speakers. The video is not really the irritant but the audio is. Sometimes you are in a spot you need to keep quiet and the audio blasts out.
CNN still uses Flash to do their videos. Many other sites have quit Flash and are using HTML5 for their videos. These steps will only work for Flash videos at CNN and a few other sites.
These directions will work in Chrome.
On the upper right of the screen in Chrome there is a button with three vertical dots. Click it. Choose Settings. Now choose Show Advanced Settings which is near bottom of the Settings page. Click the Custom Settings button in the Privacy area. Click the Block Sites from Running Flash in the flash area. Click Done. You can now go to a page or close the Settings tab.
If there is a Flash video you do want to watch, right click in the video box and the Flash video will play.