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 other options specify vertical alignment of text relative to the image on the same line. This attribute explicitly specifies the height of the graphic in pixels. It is mainly used to create custom image dimensions without physically changing the image itself.