a result of the operation of the filtering software.  These  denial screens  appear only at

the point that a user attempts to access a site or page in an enabled category.  

All four of the filtering programs on which evidence was presented allow users to

customize the category lists that exist on their own PCs or servers by adding or removing

specific URLs.  For example, if a public librarian charged with administering a library's

Internet terminals comes across a Web site that he or she finds objectionable that is not

blocked by the filtering program that his or her library is using, then the librarian may add

that URL to a category list that exists only on the library's network, and it would

thereafter be blocked under that category.  Similarly, a customer may remove individual

URLs from category lists.  Importantly, however, no one but the filtering companies has

access to the complete list of URLs in any category.  The actual URLs or IP addresses of

the Web sites or pages contained in filtering software vendors' category lists are

considered to be proprietary information, and are unavailable for review by customers or

the general public, including the proprietors of Web sites that are blocked by filtering

software.

6

Filtering software companies do not generally notify the proprietors of Web sites

when they block their sites.  The only way to discover which URLs are blocked and

which are not blocked by any particular filtering company is by testing individual URLs

6

  Indeed, we granted leave for N2H2's counsel to intervene in order to object to

testimony that would potentially reveal N2H2's trade secrets, which he did on several

occasions.  

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