[LennonCook]

Originally posted by Callum: An I wasn't converting from PNG... from BMP

Are you sure of that? Most of the images at the site you posted are either GIF or PNG.
On a side note, do not ever pay attention to the file "extension". It is useless. It is crap. It does not control what type of file it is, nor does it necesarily reflect it. To find out what type of file something realy is, look in Firefox's View Page Info (either through the context menu, or the Tools menu). On the Media tab, it will list every file on the page, and the details include the type that the file is being served as. This is usually right, because it controls (in all non-IE browsers) what the browser treats it as.