2.1.2 [DOM Level 2 - HTML] Section 1.4, Misc Object Definitions
interface HTMLOptionsCollection namedItem This method retrieves a Node using a name. It first searches for a Node with a matching id attribute. If it doesn't find one, it then searches for a Node with a matching name attribute, but only on those elements that are allowed a name attribute. This method is case insensitive in HTML documents and case sensitive in XHTML documents. Parameters name of type DOMString The name of the Node to be fetched. Return Value Node The Node with a name or id attribute whose value corresponds to the specified string. Upon failure (e.g., no node with this name exists), returns null. No Exceptions
Quirks Mode, IE7 Mode, and IE8 Mode (All Versions)
XHTML documents are not supported by the namedItem method of the HTMLOptionsCollection interface.
IE9 Mode (All Versions)
The namedItem method of the HTMLOptionsCollection interface is not case-sensitive.