constitutionally protected for adults and minors, but also that these programs are

intrinsically unable to block only illegal Internet content while simultaneously allowing

access to all protected speech. 

As our extensive findings of fact reflect, the plaintiffs demonstrated that thousands

of Web pages containing protected speech are wrongly blocked by the four leading

filtering programs, and these pages represent only a fraction of Web pages wrongly

blocked by the programs.  The plaintiffs' evidence explained that the problems faced by

the manufacturers and vendors of filtering software are legion.  The Web is extremely

dynamic, with an estimated 1.5 million new pages added every day and the contents of

existing Web pages changing very rapidly.  The category lists maintained by the blocking

programs are considered to be proprietary information, and hence are unavailable to

customers or the general public for review, so that public libraries that select categories

when implementing filtering software do not really know what they are blocking.

There are many reasons why filtering software suffers from extensive over  and

underblocking, which we will explain below in great detail.  They center on the

limitations on filtering companies' ability to: (1) accurately collect Web pages that

potentially fall into a blocked category (e.g., pornography); (2) review and categorize

Web pages that they have collected; and (3) engage in regular re review of Web pages

that they have previously reviewed.  These failures spring from constraints on the

technology of automated classification systems, and the limitations inherent in human

review, including error, misjudgment, and scarce resources, which we describe in detail

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