8. Conventions

The following conventions are used in this book:

Constant Width is used for:

Constant-Width Bold is used for:

Italics is used for:

Constant Width Italic is used for replaceable items, such as variables or optional elements, within syntax lines of code.

You should pay special attention to notes set apart from the text with the following icons:


This is a tip, suggestion, or a general note. It contains useful supplementary information about the topic at hand.


This indicates a warning or caution. It will help you solve and avoid annoying problems.

Significant code fragments, complete programs, and documents are generally placed into a separate paragraph like this:

<?xml version="1.0"?>
<!DOCTYPE window>