Bad extension? - Wha?

[matsuzo]

Ok, here is the problem. I am trying to put the URL from photobucket album thingy into a post...I used the IMG html tabs...and it comes up...prohibited extension or something like that...what in the world am I doing wrong?

[matsuzo]

this is the message I get

You are not allowed to use that image extension on this board. A valid format is: http://www.domain.com/picture.gif, an invalid format is: http://www.domain.com/picture.one.gif

btw, any response would be nice...-.-