This page was set up to show how CSS and Em sizing can be used to control the proportions of an image contained within a Flash SWF. The benefits to using Flash instead of a regular image is the ability to scale text without distortion, and the fact that it handles the image resizing better than typical browser rendering, which makes the image very jagged when changed from its original dimensions. This also allows the possibility of animation scaling to enable those with vision impairments to view it at a size that is more legible to them.
To ensure that all users have the same experience, a fall-back image is contained within the <object> tags. If Flash Player is not installed, it will use a backup image, which is also styled in Ems and will resize in the same manner, albeit not as attractively as when done as Flash. The drawbacks to using this method are the necessity for software that can output SWF files, and having to create both a SWF and a fall-back JPG file. I suppose that it could be done with an external XML file, but that is just add another step to get it to work. Ideal situations for using this technique would be for rich media that needs to be accessible to the visually impaired, or applying Em sizing to sIFR headline text so that it resizes proportionally to all other page copy.