http://www.perlmonks.org?node_id=206928


in reply to Re: On CSS and other machinations.
in thread On CSS and other machinations.

For some reason, Netscape (or Mozilla) doesn't allow for underscores in names of CSS or 'div' or any DHTML 'id' or 'name' attribute after their version 6 browser for Netscape and any Mozilla (that I'm aware of.)

The reason Netscape & Mozilla don't allow "_" is that it's not legal CSS. See the appropriate dull bit from the spec.

Not a bug :-)

I lied. Underscores have been allowed since the 1998 errata.