Goldtrap, its a matter of the correct URL. Look carefully, the first one ends as * * picture.gif * *the second one ends as *picture.one.gif
The system thinks that the file extention is .one and not .gif so it spits it out as invalid. Whenever you get error messages like that go back and double check that every single character you type is correct. URLs are typo, and case sensative. Make a mistake and the whole thing is bad.