The Doctor What writes:

<dtml-call expr="RESPONSE.redirect('index_html?message=Link+added&url_id='+url_id)">

Zope complains about a builtin... Apparently "url_id" is not a string but something else.

You may try "_.str(_.render(url_id))" instead of "url_id". "_.render" would call the object, if it were callable. "_.str" would turn it into a string. Of course, one of these operations may not be necessary. Dieter