MACROMEDIA STUDIO 8-EXPLORING STUDIO 8 Manual page 220

220 Tutorial: Building Your First Flash Application
4.
In the Document Properties dialog box, enter 700 in the width text box
and 150 in the height text box, and then click OK.
Flash automatically inserts the px (for pixel) after the number.
The Document Properties dialog box
5. In the Timeline, click the value in the Zoom menu and enter 75%.
This makes it easier to see your entire document in the
Document window.
Press Enter (Windows) or Return (Macintosh).
6. Save your work.
For more information about setting document properties, see
opening a document and setting properties"
"Creating or
in Using Flash.