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engine - 6:39 pm on Nov 11, 2002 (gmt 0)
I read the page provided [alltheweb.com] and it does say it's not 100% accurate. I can only guess that it's a filter looking for the most common words, phrases and filenames that have been defined by FAST as "offensive." If those words appear on your site it would explain the missing pages when the filter is on. I doubt we'll get to know the list, however, you could build your own list by looking for the missing pages and compiling the possibilities into a spreadsheet or database.
Hi and welcome to WebmasterWorld.