They may appear in any order. Attribute names are always case-insensitive.
Attribute values are generally case-insensitive.
A browser may use this information to filter out non-conforming files when prompting a user to select files to upload. Comma-separated list of MIME types. A single character is used as the value of this attribute. A single, case-insensitive alphanumeric character from a browser's character set. This is a stand-alone attribute which tells the browser that content in the field may not be modified by the reader.