They may appear in any order. Attribute names are always case-insensitive.
Attribute values are generally case-insensitive.
A single character is used as the value of this attribute. A single, case-insensitive alphanumeric character from a browser's character set. A recognized RFC 2045 language character set string. The coordinate system for Client Side Image Maps originates at the top, left corner of the image and values grow larger as you move down and to the right. Either this attribute or the NAME attribute MUST be present in the A tag.