It was originally written in DocBook/XML and converted to AsciiDoc by Gerald Combs.
You will find some specially marked parts in this book:
|This is a warning|
You should pay attention to a warning, otherwise data loss might occur.
|This is a note|
A note will point you to common mistakes and things that might not be obvious.
|This is a tip|
Tips are helpful for your everyday work using Wireshark.