Deprecated ISO 639 (rfc 1766)

"A deprecated element or attribute is one that has been outdated by newer HTML constructs. Deprecated elements are defined in the reference manual in appropriate locations, but are clearly marked as deprecated. Deprecated elements may become obsolete in future versions of HTML.

We strongly urge authors to avoid deprecated elements and attributes. To this end, we provide alternatives to them when appropriate in the specification.

User agents should continue to support deprecated elements for reasons of backward compatibility." (excerpted from W3C HTML 4.0 specification)