In HTML, you can declare the Character Set for the file. Here's example of setting it to be UTF-8 (Unicode):
<meta http-equiv="Content-Type" content="text/html;charset=utf-8">
If you don't understand what is Character Set and Encoding, see: UNICODE Basics: What's Character Encoding, UTF-8, and All That?.
Once you declared your character set, you can have characters from that character set in your HTML file.
UTF-8 (Unicode) contains all the world's language's characters. Here is a sample of characters from Unicode:
“ ” ‘ ’ € £ ¥ © ® ™ ¶ † ‡ — é å ø è ü θ π α β → ← ↑ ↓ ↔ ↗ • ‣ ♥ ★ ± ≤ ≥ ≠ ≈ ° ∑
For more examples, see: Sample Unicode Characters.
Another way to show special characters in your file is by so-called “character entity”.
For example, the bullet symbol • is Unicode character number 8226. In HTML, you can write it as •.
The number 8226 in hexadecimal is 2022. Sometimes you only know the hexadecimal number of a character. You can write it using hexadecimal like this •.
For some commonly used characters, HTML provides “named entity” for them. For example, the bullet character can be written as •.
For a complete list of named entities, see: HTML/XML Entities List.