Lots of script errors after copying and pasting

I was trying to insert text as similar to this project: http://playcanv.as/p/KqqOGvVi/?overlay=false
Into my project: https://playcanvas.com/project/473132/overview/moon

This is the error log I get (same as the screenshot):

I have no idea how to debug this, thoughts?
I just copied and pasted, there are 4 files, 1 simple CSS styling of the left upper corner card with text and a button, 1 HTML file with the content and some divs, 1 javascript handler for the CSS and one for the HTML (and I have no idea what they do). I do know CSS and HTML well but I don’t know much about javascript.

have you selected the html and css files as assets of the htmlhandler and csshandler?

You have an Entity called html+css, with a script component that has 2 scripts - The htmlHandler and the cssHandler. These scripts expects a script attribute - the first expects an HTML asset and the second a CSS asset. So in the Editor you need to drag and drop those assets to the respective slots of the script component.

I also recommend going through the user manual to get accustomed to PlayCanvas:

http://developer.playcanvas.com/en/user-manual/

It worked!
It seems that the error was indeed related to what Vaios mentioned.

Vaios, would you mind explain a little bit of what these handlers are doing?

Which bit is unclear to you? I think you might wanna look in the tutorials for detailed instructions for that kind of stuff!

ok I will check in the tutorials