You can re-save it or rename it, whatever you wish, but when you do, either right click and "save as" brownie.gif or right click on the file in your computer "rename" and rename it WITH the .gif extension. I know that sounds complicated....I think that's what must have happened. Often times when you save things online you have to specify their file extension or the computer doesn't know what the file is or what to do with it. I checked your blinkie again and it is a valid .gif file and it works fine and should totally work on this site.
Try that, and if you still need help we'll figure it out, dont' worry! LOL.
