Bill, You don’t have to use the second tag, unless you build different content for different english versions on your site.
Here are some sample language codes:
“en”: English
“en-US”: the U.S. version of English.
“en-cockney”: the Cockney version of English.
“i-navajo”: the Navajo language spoken by some Native Americans.
“x-klingon”: The primary tag “x” indicates an experimental language tag
more: http://www.w3.org/TR/html401/struct/dirlang.html
Yes it does matter. There is a way to pass the validator.
