Calculator
html to pseudo-element
Symbols in HTML
Entities, symbols & characters have four methods of reference:
Named, Decimal, Hexadecimal, and Unicode, but only the Decimal form is reliable across browsers and platforms.
To use decimal notation encoded in UTF-8 insert
<meta charset=“utf-8”>
as the first line in the <head> of your document.
UTF-8 Encoding
The name is an acronym of Unicode Transformation Format – 8-bit.
Unicode is an abbreviation of Universal Coded Character Set.
It is a Character encoding capable of encoding all characters,
1, 114, 112 in total.
It is the dominant character encoding for the world wide web, accounting for 88.9% of web pages in April 2017.
En & Em
Two useful spaces in the HTML repertoire are the en space   and the em space  .
Both are visibly wider than a normal space, as mandated in the official HTML specification.
Outer spaces
Sometimes in typesetting you need to provide a hint that the computer can break a long word in a particular position without any other interpretation or visible indication.
This is the zero width space : ​
Its twin is the zero width no-break space :  which can be used to keep a word from breaking at that point.