Re: checked attribute for a checkbox input

>> Let me clarify:  Is the necessity of the use of :if* documented anywhere?

You can find it mentioned here.   Search for if*
and you'll find the documentation and an example:

http://www.franz.com/support/documentation/6.2/doc/aserve/htmlgen.html




>> And in what other similar contexts is it necessary to use it?

It's useful in cases where you only want to add an attribute value
to an element rarely and let whatever default value is in effect
be used otherwise.