Before you submit, check the url to make sure it works... many (if not all) sites use case-sensitive filenames, meaning if your filename is called joesscript.zip... don't put http://site.com/JoesScript.zip as the URL.
Avoid using common file names.
Common file names such as file.zip, mirc.zip, script.zip, mp3.zip, setup.exe, whois.mrc, etc. are likely being used by other files.
If your file on a free web site?
I encourage you to use GeoCities, Xoom, and Spaceports. These three work great and are usually faster than the others.