one of the documented procedures in this installation of the ACS
ad_return_complaint   exception_count   exception_text
What it does:
Return a page complaining about the user's input (as opposed to an error in our software, for which ad_return_error is more appropriate)
Defined in: /web/philip/packages/acs-core/defs-procs.tcl

Source code:

    # there was an error in the user input 
    if { $exception_count == 1 } {
	set problem_string "a problem"
	set please_correct "it"
    } else {
	set problem_string "some problems"
	set please_correct "them"
    ns_return 200 text/html "[ad_header_with_extra_stuff "Problem with Your Input" "" ""]
<h2>Problem with Your Input</h2>

to <a href=/>[ad_system_name]</a>


We had $problem_string processing your entry:
Please back up using your browser, correct $please_correct, and
resubmit your entry.
Thank you.