The symbols CSS descriptor of the @counter-style at-rule is used to specify the symbols for creating counter representations in the specified counter system. Specifying this descriptor is mandatory when the value of the system descriptor is cyclic , numeric , alphabetic , symbolic , or fixed .

Special characters in CSS Either you use the Unicode code point — for example, the plus sign ( + ) is U+002B, so if you would want to use it in a CSS selector, you would escape it into \2b (note the space character at the end) or \00002b (using exactly six hexadecimal digits).

Incorporating symbols into HTML can be done using HTML entities, which are special strings of characters starting with an ampersand (&) and ending with a semicolon (;).

In CSS, identifiers (including element names, classes, and IDs in selectors) can contain only the characters [a-zA-Z0-9] and ISO 10646 characters U+00A0 and higher, plus the hyphen (-) and the underscore (_); they cannot start with a digit, two hyphens, or a hyphen followed by a digit.