The canvas is set to a default size; because I prefer to work at standard sizes and aspect ratios
for web production, I'm going to change my canvas size from the default of 550 pixels
wide x 400 pixels high to a smaller size of 320 x 240. I'm going to do this by clicking the button on the Properties tab--the panel just below the canvas and working area--that displays the canvas size; this will open a new pop-up window containing the document's properties. For right now you only need to worry about three things: the document size, the background color, and the frame rate
I'm going to adjust my size to 320 x 240 by manually entering the values in the spaces provided, use the color picket to select a light blue background, and leave the frame rate set at 12 fps (frames per second). This is the default frame rate for web production; for television and other media production, it can go as high as 30 frames per second. 12 is all that you really need for Flash animation for the web; it still allows a consistent flow of motion, but avoids raising your file sizes by adding extra frames.