Allows authors to specify a lower resolution image to be shown while the actual image is downloading.
If the src property is set in code, the new URL starts loading into the image area and aborts the transfer of any image data that is already loading into the same area. If you want to alter the lowsrc property, you must do so before setting the src property. If the URL in the src property references an image that is not the same size as the image cell it is loaded into, the source image is scaled to fit.
Microsoft Developer Network: [Windows Internet Explorer API reference Article]