Vimeo files won't go full screen on Firefox, Edge and Safari

Marina,

If you've never heard of an iFrame then it's likely that you have very little experience with web programming. If so, the solutions offered in that Captivate Forum post that you cited above are likely to be too advanced for you to implement.  You might be wise to contact Dave at TLC Media Design, the (very talented) programmer who suggested the coding fix.  I'm sure he would be willing to help you in exchange for a very reasonable fee to cover his time.

You can learn about iFrames here: HTML Iframes

These are usually used in websites to display content on one page that actually originates from a totally different website or server.  That's why iFrames are often used to display videos from YouTube or Vimeo.  But in order to prevent people from illegally displaying someone else's content without their permission, some websites implement code that will disable any content being displayed in an iFrame.

The CPM.js file is a file created by Captivate when you publish a project to HTML5 output.  It contains the majority of the code information and references related to the various images and objects that appear on slides throughout the project.  It's likely to be the largest single file in the entire HTML5 output, so in a large project it can be many megabytes in size and contain thousands of lines of code.  Modifying this file is not for the faint-hearted or beginner.  Any error would mean your output will stop dead and you'd need to re-publish again to generate another CPM.js..