[JKT]

Hmm, if you force Preview to open the .php file for the avatar, it will open it and Get Info shows it to be a .gif

Graphic Converter will open it to.

Seems to be some issue with the way OmniWeb is copying the file to the clipboard (or the way the Finder is identifying it when dropped).

FWIW, you can also ctrl/right-click the image and select one of the [Image>Download Image options as a workaround. This will initially download a .php file but it quickly gets re-identified as a .gif file.