The standard webinator search is always case insensitive unless you use
the REX pattern matcher and specify respect case. REX should only be
used in conjunction with another normal search term. Also, the URL is
not included in the normal search.
If you want to search by URL, you need to be using the matches operator
on the Url field of the html table. Search the message archive at
http://www.thunderstone.com/texis/webinator/listproc/
for
url matches
for some discussion of Url searching.