+<sect2 renderas="sect3">
+<title id="knows">How does <application>Privoxy</application> know what is
+an ad, and what is not?</title>
+<para>
+ <application>Privoxy</application> processes all the raw content of every
+ web page. So it reads everything on each page. It then compares this to the
+ rules as set up in the configuration files, and looks for any matches to
+ these rules. <application>Privoxy</application> makes heavy use of
+ <quote>regular expressions</quote>. (If you are not familiar with regular
+ expressions, it is explained briefly in <ulink
+ url="../user-manual/appendix.html">the user manual</ulink>.) Regular
+ expressions facilitate matching of one text string against another, using
+ wildcards to build complex patterns. So <application>Privoxy</application>
+ will typically look for URLs and other content that match certain key words
+ and expressions as defined in the configuration files. For instance a URL
+ that contains <quote>/banners</quote>, has a high probability of containing
+ ad banners, and thus would be a prime candidate to have a matching rule.
+</para>
+<para>
+ So <application>Privoxy</application> will look for these kinds of obvious
+ looking culprits. And also, will use lists of known organizations that
+ specialize in ads. Again, using complex patterns to match as many potential
+ combinations as possible since there tend to be many, many variations used by
+ advertisers, and new ones are being introduced all the time.
+</para>
+</sect2>
+
+<sect2 renderas="sect3">
+<title id="mistakes">Can <application>Privoxy</application> make mistakes?
+This does not sound very scientific.</title>
+<para>
+ Actually, it's a black art ;-) And yes, it is always possible to have a broad rule
+ accidentally block something by mistake. There is a good chance you may run
+ into such a situation at some point. It is tricky writing rules to cover
+ every conceivable possibility, and not occasionally get false positives.
+</para>
+
+<para>
+ But this should not be a big concern since the
+ <application>Privoxy</application> configuration is very flexible, and
+ includes tools to help identify these types of situations so they can be
+ addressed as needed, allowing you to customize your installation.
+ (<link linkend="badsite">See the Troubleshooting section below</link>.)
+</para>
+
+</sect2>
+
+
+<sect2 renderas="sect3" id="browsers2"><title>My browser does the same things as