Geocities are dead. But c.gif is still there. Move your mouse over the area above that looks empty to feel it. Click on it to see where it comes from.
Early web designers always had a clear/empty image file in the graphics folder of their projects. Usually it would be called clear.gif. Mine was — 0.gif. And most commonly it would be just 1 pixel of nothing. The one on Geocities is 10×10 pixels.
Clear gifs were irreplaceable in the world of pre-CSS layouts. Invisible and small graphics could be stretched in width and height, keeping visible elements of the page on desirable distance.
On the page where I found Geocities’ c.gif, it was used in a very clumsy way: 23 clear gifs in a table row to make an invisible line of 751 pixels. A human being wouldn’t do it. Yahoo! PageBuilder did.