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In Serialization 7.1 list item 1: The serializer MUST serialize an attribute with the name xmlns whose value is equal to the namespace URI of the element node, unless an ancestor element in the serialized result already has an attribute named xmlns[^]with the same value, and no interverning element has an attribute named xmlns with a different value. (A) missing space at [^] (B) misspelling of intervening
I've fixed the typo, but I don't see xmlns without the trailing space. Which browser are you using?