Can class names begin with a hyphen followed by a number?
This SO answer says [1]:
> a name must begin with an underscore (_), a hyphen (-), or a letter(a–z), followed by any number of hyphens, underscores, letters, or numbers. There is a catch: if the first character is a hyphen, the second character must be a letter or underscore, and the name must be at least 2 characters long.
[1]: http://stackoverflow.com/a/449000
Which references the CSS Grammar spec [2].