If you use the default wrapper created by Flex Builder, the IFrame's width is set to 22 pixels by default.
I really wish there was an easy way of discovering shortcuts for OS X.

On Windows, I use the excellent Wamp to set up a local development environment with Apache, MySQL and PHP. On the Mac, I just discovered MAMP which lets me do the same thing.
The xinf (pronounced: 'sinf, acronym for "xinf is not flash") project aims to provide a unified platform for cross-runtime GUI development. It will enable you to develop graphical interfaces and "rich internet applications" that run on the Adobe Flash Player, within web browsers supporting JavaScript, and on a cross-platform player built on neko and OpenGL, from one and the same codebase. Most of the cross-runtime magic is provided by Nicolas Cannasse's "haXe" language and compiler.
Xinf is currently slated to have three components:
Here's what they say: