For example, HTML code expects certain elements (there are others, but I can't think of what they are which is why I want to find a reference - like a 'green card' that we old mainfraime programmers so coveted). The following is sort of what I'm looking for but showing all elements exhaustively and where they should be placed:
<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8" />
<meta name="viewport" content=
"width=device-width, initial-scale=1.0" />
<title>Structure of HTML Document</title>
</head>
<body>
<!-- Main content of website -->
<h1>GeeksforGeeks</h1>
<p>A computer science portal for geeks</p>
</body>
</html>
Obviously, there are a host of 'words' that might be added to the above example; but I hope it gives an idea of what I'm looking for. In the example, a user could hover his mouse over a particular element and see a block pop up that would define the element and provide useful information about how it's used and what qualifiers it might take with each of those qualifiers having a hover property explaining them in turn. One might think of this as a dictionary for the language in questions showing all the words in that language and how they are used with any inter-dependencies noted.
If one looks at the statement, above, <!DOCTYPE html>, one could hover over !DOCTYPE and a box would appear stating, "All HTML documents must start with a <!DOCTYPE> declaration plus a list of qualifiers in addition to html that might be used." Hovering over 'html' would cause a box to appear identifying it as "Hyper Text Markup Language."
The declaration is not an HTML tag. It is an "information" to the browser about what document type to expect.
Another example: The CSS element DISPLAY can, AFAIK, take only three qualifiers - block, inline, and inline-block. (If there are others, I don't know what they are. Following tutorials one only learns what the tutor exposes in a given module and rarely gets to see ALL of the information about a particular language element. A set of references would make learning far easier, IMO.
I'm looking for a reference for each of the 3 languages cited.
If anyone knows of the existence of such reference materials, I'd be much obliged to know of them.
