You have a landing page that needs to show some code for the user interact with. CodeFlask makes a lot of sense here.
You have an API sample and want your visitors to copy/edit it for a better understanding. CodeFlask is the way!
You want to share code snippets but giving the possibility to users edit and play with this code. Yo CodeFlask bro.
You can use CodeFlask for pretty much anything not involving a lot of code. You can learn more about why it should not be used with big chunks of code bellow.
CodeFlask isn’t intended to run big chunks of code and thus SHOULD NOT be used for web IDEs and big files.
If all you want is to highlight code on your page, you should use the plugin that gave origin to CodeFlask and that is focused only on syntax highlight: Prism.js.
CodeFlask was made using today HTML5 features and may present rendering issues on older browsers.
CodeFlask was made aiming small pieces of code and does pretty well with those, for large chunks of code you may want to take a look at a robust solution, such as CodeMirror.