Hello Michael,
There are various sample apps that deal with HTTP calls, and, one of them, the Database sample, even when appear quite simple, it's a complete CRUD app, which allows to Create, Read, Update and Delete data from a server database. Basically the app made HTTP calls and deal with the server's response. So I think you must try to be a bit more specific, around the possible problem that you get.
You talk about HTML tags, Javascript, Ajax... and yes... we can use these stuff in AB, since we are talking about HTML, CSS and Javascript apps. But I am not quite sure that this is your problem. You mention this URL: "https://cherithwells.com/tester.php", and, certainly that URL offers certain JSON response, however, in fact is a wrong response, which can cause problems to be processed:
As you can see above, the response is a JSON object, but, just at the end, the "worker!" string appear... well... that string in that JSON response probably cause problems to be processed. On the other hand, process the "{"a":1,"b":2,"c":3,"d":4,"e":5}" response can't be more easy. Since the response is a JSON object, we can directly access to that object properties, for example:
I hope the above can help you in some manner, but, please, go ahead if you have any further question.