Some links regarding this matter:
https://bugzilla.mozilla.org/show_bug.cgi?id=28293
http://www.hunlock.com/blogs/Deferred_Javascript

Here’s some W3C for you, Mozilla boy.

defer [CI]
When set, this boolean attribute provides a hint to the user agent that the script is not going to generate any document content (e.g., no “document.write” in javascript) and thus, the user agent can continue parsing and rendering.

HTML 4.01 DTD:

<!ATTLIST SCRIPT
charset %Charset; #IMPLIED -- char encoding of linked resource --
type %ContentType; #REQUIRED -- content type of script language --
src %URI; #IMPLIED -- URI for an external script --
defer (defer) #IMPLIED -- UA may defer execution of script --
event CDATA #IMPLIED -- reserved for possible future use --
for %URI; #IMPLIED -- reserved for possible future use --
>

HTML validator output:

Line 15, column 48: value of attribute “DEFER” cannot be “TRUE”; must be one of “DEFER” (explain…).

<script type="text/javascript" defer="true">

That said, the HTML 4.01 standard does not explicitly state a behavior, and does not require the user agent to recognize the attribute:

“When set, this boolean attribute provides a hint to the user agent that the script is not going to generate any document content (e.g., no “document.write” in javascript) and thus, the user agent can continue parsing and rendering.”

This is a poor specification, because an ambigious load order will cause problems if there are interdependencies between the script elements.

Great to see a complete idiot trying to talk smart and then find a correction right below it. The boolean operation is evaluated on the presence of a defer-attribute, meaning you can pretty much put anything as a value. It’s not evaluated by the string (“true”) in your value, since that is a STRING.

The fact that you use a value at all is that XHTML does not allow properties without values on elements, same thing with and so on.

YOU do understand the concept, right?