CSS identifier naming

The commonly used identifiers in the general write CSS are named in English word combinations.

One day I met someone asking if you could use the name _1. Then dumbfounded, did not think about whether there is such a naming method

In CSS, identifiers (including element names, classes, and IDs in selectors) can contain only the characters [a-za-z0-9] A nd ISO 10646 characters u+00a0 and higher, plus the hyphen (-) and the underscore (_); They cannot start with a digit, both hyphens, or a hyphen followed by a digit. Identifiers can also contain escaped characters and any ISO 10646 character as a numeric code (see next item). In CSS identifier naming You can also use hyphens (-) and underscores (_) with characters that contain characters (a-za-z0-9) and ISO 10646 character sets, and the starting part cannot be a number, or two hyphens "-" or a "-" hyphen followed by a number. Identifiers can also contain escape characters and any ISO 10646 character numeric code.

Special characters in CSS include:!, ", #, $,%, &, ', (,), *, +,,,-, .,/,:,;, <, =,;,?, @, [, \,], ^, ', {, |,}, ~
These characters need to be escaped to be used for naming, preceded by a backslash "\" Escape to remove the specific meaning of these characters.

<style>. _1{Color:#f90;Border:1px solid #f90;padding:20px;}    .\#{Color:#f00;Border:1px solid #f00;margin:20px Auto;}</style><Divclass= "_1">Identifier naming</Div><Divclass="#">Need to escape characters</Div>

CSS identifier naming