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. The value of an ID attribute belonging to a form field in the current document. In addition to the specific attributes above, there are more generic attributes which have been organized into three separate categories.