The Element.attributes property returns a live collection of all attribute nodes registered to the specified node. It is a NamedNodeMap, not an Array, so it has no Array methods and the Attr nodes' indexes may differ among browsers. To be more specific, attributes is a key/value pair of strings that represents any information regarding that attribute.
The Element.getElementsByClassName() method returns a live HTMLCollection containing all child elements which have all of the given class names. When called on the document object, the complete document is searched, including the root node.
The Element.getElementsByTagName() method returns a live HTMLCollection of elements with the given tag name. The subtree underneath the specified element is searched, excluding the element itself. The returned list is live, meaning that it updates itself with the DOM tree automatically. Consequently, there is no need to call several times Element.getElementsByTagName() with the same element and arguments.
The HTML Center Element (<center>) is a block-level element that can contain paragraphs and other block-level and inline elements. The entire content of this element is centered horizontally within its containing element (typically, the <body>).