Hehe fair enough. But that's a big answer you asking for... and Im not myself that savvy.
You should learn at least a bit of html (dead easy), css (the design part), and javascript (the only real progrmming here, the other two are more like layout languages). The old classic way was the w3schools.com, but there should be thousands of alternatives nowadays. stackoverflow.com is also very useful, more like a Q&A forum.
Here's a very old mockup I had somewhere, is only half sketched but will do as an example. (Not a very good one concerning txt blurriness, cause I used some css text shadow I think. And also seem to take ages to load. Oh well). I seem unable to write a link properly in this damn forums so here's the address:
WEB c2web.netlify.com
The capx ( drive.google.com/open ) is unimportant here, it only contains the animated background, and this following line of code:
which calls the function “carga()”. But this function is not inside the construct project...
When you export a html5 project from C2, what you get is a webpage containing your game, like this:
ZIP drive.google.com/open
The file index.html is always the start (in this case the only) page in any website. Here is where the game “happens”. And here I built a simple structure, with a menu on top and some text in blocks (called “divs”; mind the text is not in the capx), and made the game “happen” in the background. You can edit html files with any text editor, but there are many (brackets, notepadC++) specially designed for coding. If you open index.html you'll see this structure, and also that “carga()” function that I called from inside the capx. What this function does is set the whole content (the aforementioned “structure”) visible, as I set it invisible by default. Why? Cause I dont want the text being shown while the game (the background of my site) is loading. Similarly, you can call a Construct function from the html (change music or images when a link is hit, for example). Functions are a straight way to interact capx and html, and a very powerful one too, as they let you do nearly anything.
I've used myself construct to make simple presentations and portfolios, but those were no webpages – I rather called them “online apps”. And people seemed impressed lol.