Some time between Merlin beta (build 65) and the current beta2 build (77), javadoc seems to have gotten a bug where the "Serialized Form" link for a serializable class is omitted if the class's comment does not have any @see tags of its own to put in the "See Also" section.

For example, compare the following, which I presume were generated using a recent beta2 version of javadoc:

http://webwork.eng.sun.com/j2se/1.4/docs/api/java/lang/Byte.html
http://webwork.eng.sun.com/j2se/1.4/docs/api/java/lang/Character.html

Both Byte and Character are serializable (and both have entries in the big serialized form page), but only Byte's generated documentation page contains a link to the appropriate section of the serialized form page, presumably because it also has an @see tag (for java.lang.Number).

The Merlin beta generated documentation can be found here, at least at the time that this bug report was filed:

http://java.sun.com/j2se/1.4/docs/api/java/lang/Byte.html
http://java.sun.com/j2se/1.4/docs/api/java/lang/Character.html

Notice that for beta, the documentation page for Character (correctly) includes a link to the serialized form page in its "See Also" section. (And even after beta2 ships, the corresponding pages on java.sun.com for 1.3 will show the correct link being there.)

(I've perused through the documentation for a few dozen serializable classes on webwork.eng/j2se/1.4/docs/api, and well as that for many serializable classes in a different product, and in all cases, the serialized form link was present if and only if the class doc had any other items in the "See Also" section, so I'm fairly confident in concluding that relationship regarding this bug.)