XML Namespace: An abstract container for various items; each item within a namespace has a unique name, but the namespace allows disambiguation of items with the same name that are in different namespaces.
The XML Namespace (xmlns) Attribute
The XML namespace attribute is placed in the start tag of an element and has the following syntax:
When a namespace is defined in the start tag of an element, all child elements with the same prefix are associated with the same namespace.
Note: The parser does not use the address (URL) value ( which is used to identify the namespace information). The only purpose is to give the namespace a unique name. The URL is not a valid endpoint as such… it is just a qualifier. However, very often companies use the namespace as a pointer to a real Web page containing information about the namespace. Try to go to http://www.w3.org/TR/html4/.