We can use single-pixel GIF files to construct images. Because Netscape automatically scales images to the specified width and height, you can create rectangles of various dimensions from a 1 ¥ 1 GIF image of a particular color.
This technique is especially useful for creating dynamic bar charts; but beyond that, its applications are very limited. I won’t cover this technique here, but I encourage you to experiment with it on your own.
Ananova 