When a tag is parsed, its attributes are read in one of two ways—literally, or interpretively. Similar to
existing conventions in a variety of languages, defining a value in single-quotes (e.g.,
name='value') causes the contents of the value to be parsed literally, regardless of the
characters between quotes. Using double-quotes causes its contents to be parsed interpretively, meaning that some characters
will be treated in special ways.
Specifically, these special characters are the dollar sign ($), the at sign
(@), and the ampersand (&). These characters correspond
to variable substitution, object variable value substitution, and entity substitution, respectively.
Value substitution is the process by which a variable, cookie, object, or entity's
substituted for its syntactically referenced
. This occurs at the name's original location in any
arbitrary string of characters.