anastasia: I'm afraid Rose did not get your drift, neither did she actually visit Geocities to correctly answer your query :)
That 3GB is in fact the traffic that they allow you to have per month, and they'll be watching dutifully over it every single hour - if your page is too popular, down it goes and noone can see it again until next month!!!
The actual space that Geocities Free gives you is a disappointing 15MB - OK, it's not too bad, but I bet it looks bad compared to 3GB, right? :)