If you can see the lesson below, your browser meets the requirements.
Some courses require Flash.
If you cannot see the Flash animation below (in the red box), please visit https://helpx.adobe.com/flash-player.html to installed and enable Adobe Flash.
All other browsers: https://enableflashplayer.com
If your still having problems with course lessons not being able to run Flash (i.e. you see a red background with Flash icon in the center or if it has been 'blocked'), be sure to enable/allow Flash through your browser.
On newer versions in Chrome, select the "Site settings" (Image 1) and Allow Flash on the new tab that appears (Image 2) - for full instructions: please refer to the following link: https://support.google.com/chrome/answer/6258784.
In older Chrome versions, this is easily done by clicking on the lock icon () next the URL and selecting Allow for the Flash option (see Image 1 below).