This site is run on the Everything Engine which run by The Everything Development Company(which is stated on the bottom of every page here) - check out the site. It has documentation as well as the source.

If you're talking about the URL query string and CGI - I'm not sure... but here is some information from the CGI documentation:

MIXING POST AND URL PARAMETERS  
   $color = $query->url_param('color');


It is possible for a script to receive CGI parameters in the URL as we
+ll as in the fill-out form by creating a form that POSTs to a URL con
+taining a query string (a "?" mark followed by arguments). The param(
+) method will always return the contents of the POSTed fill-out form,
+ ignoring the URL's query string. To retrieve URL parameters, call th
+e url_param() method. Use it in the same way as param(). The main dif
+ference is that it allows you to read the parameters, but not set the
+m. 


Under no circumstances will the contents of the URL query string inter
+fere with similarly-named CGI parameters in POSTed forms. If you try 
+to mix a URL query string with a form submitted with the GET method, 
+the results will not be what you expect.
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Oops.. I think I possibly misread the question. My apologies. Please delete if so.