Evolution
XHTML version 1.0
The W3C recommendation for XHTML version 1.0 is to combine the lang attribute with xml:lang attribute, as follows for example:
Lang and xml:lang Attributes
The combination was recommended because of a deficiency in browers' capacities to process the xml:lang attribute. You may well want to continue to combine the two attributes.
XHTML version 1.1
The lang attribute has been dropped from XHTML version 1.1 and will not persist in version 2. The xml:lang is used on its own in these further versions of XHTML.
