I do regular presentations, although mainly security related, for the non-technical staff at my workplace. I have a few comments, stemming from personal opinion and anecdote, that you should feel free to take or leave.
My comments are hopefully on-topic, but I'm not positive on the exact scope of your presentation nor the technical literacy of the people you are presenting to. A web 101, to me, is rudimentary stuff. From your general ideas however, it seems like this is a bit higher level than a Web 101. I'm not sure if your ideas are just ambitious, or if this is a bit more than a 101.
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If this is Web 101, and not Programming 101, I would advise skipping over any sort of programming whatsoever. Even though it can be presented in a logical and understandable fashion, if someone has trouble understanding the basics of web, I do not believe they are going to enjoy even surface level programming. Perhaps just an extremely brief overview (and/or definitions) would suffice. "X is a programming language, usually used for Y, and it helps accomplish Z". A marketer (generally) doesn't need to know what a function is doing or how it does it, they want to know how it helps them.
Although a brief history of computers might be good to introduce the presentation, I wouldn't spend much time on it. I have found that most people I have presented to really aren't interested in the history or development of computers or the internet. They want to know what's happening now.
Emerging technologies would be good, but I would avoid getting too specific. I would recommend focusing on what the technologies will allow them to do, rather than focus on how the technology does it. "We've all heard the buzzwords AI, ML, etc. As they advance, and as costs come down, here are some things we could leverage the technology for...". Emphasizing what the technology will do for your marketers and advertisers will have them much more excited than trying to explain what is happening mathematically or programmatically.
I find the key with giving a technical presentation to a non-technical audience is to not cover too many topics, even if they are just overviews. Rather, a slightly more in-depth and much more focused presentation has always yielded me better results. My first presentations tried to cover everything from passwords, to phishing, to viruses, etc. They were not very successful.
What specifically is the goal for your presentation? If you have to choose one thing for your audience to walk away with, what would it be? Center your presentation around that, and perhaps touch on some tangential topics.
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Personally, given the goal of "demystify the web" only, and assuming a completely non-technical audience, I would structure my presentation like this:
Extremely brief history of computers, using a story instead of technical. As my presentations are usually security related, I like to start with the 1903 telephone hack, where a gentleman named Nevil Maskelyne interrupted a public presentation of a "secure" telephone line, by sending insulting Morse Code messages during the presentation [1]. It usually gets some laughs, is relatable, and segways nicely into how things have evolved since.
Next I would focus on an overview of browsers and websites. Something fairly short, but lays the groundwork for the meat of the presentation.
Since your audience is mainly marketing / advertising, the bulk of my presentation would be focused on the (slightly) more technical side of those fields. If they are familiar with SEO, you could discuss what is happening on the back end. Perhaps talk about web scraping, indexing, linking, analytics and tracking, etc. Anything that might help them do their job better.
That might lead into how AI/ML and all the other buzzwords might help them with SEO, or writing copy, etc. Again, not focusing on what AI is, but how AI might help them.
Just my 2c, I'm sure whatever you come up with will still be a great help!
[1]https://www.newscientist.com/article/mg21228440-700-dot-dash...
Edit: Some afterthoughts. A quote comes to mind, but I cannot find the exact one. It's along the lines of "Using a simple, but somewhat wrong analogy is much better than a technically accurate, but confusing one". Secondly, I would advise having your main goal be to teach them something that they can use in their day to day. Something that affects them, personally. You want them to be invested in what you have to say, and the best way to accomplish that is to show them what your presentation can do for them during their day to day.