What does that discreet yellow writing in the Craigslist Adult postings mean?

My B/F and I were joking and went to the Adult section of Craigslist.com checking out a few things. Most of what we saw was ludicrous and funny. But underneath all of them were writing in yellow, barely recognizable. Highlighted what was written seemed to be nonsense or sections out of a book. I was wondering if anyone knew what it was. Is it put there as a joke? A code?