Transparent JPEG??? One I didn't declare!

With the new version of Firefox (FF4.0), the "Free Monster" image (in my earlier project (http://www.codingforums.com/showthread.php?t=152297)) appeared, suddenly as a transparent graphic. This is very strange, considering it is a JPEG and no transparent pixels were ever declared, at the time of saving!
If anyone could offer an explanation for this, I'd be grateful. The black background of the image is completely transparent and I could see other elements through it, such as the H1 or the other image, when it was accidentally positioned over them. How can this be? I thought only GIFs and PNGs were capable of transparency!

Is this a new bug (or feature) of Firefox?

Yours, the ever puzzled
http://i183.photobucket.com/albums/x103/Doctor_Varney/signature.gif

I'm not quite sure what's going. For starters, Firefox 4 doesn't exist, and JPEGs don't support transparency. Check your css and make sure that isn't effecting anything.

Offtopic: I'm not going to post ever again... 666 FTW!

We need a link to your site to tell you whats really going on.

JPEGs don't support transparency, maybe you have just changed the file extension? But kept the file itself as a png?

Maybe the file extension really is a PNG, but has been changed to .jpeg somewhere.
Once again, JPEG's don't support transparency.

Offtopic: I'm not going to post ever again... 666 FTW!
Ha!

I'm not quite sure what's going. For starters, Firefox 4 doesn't exist

Ah, but I am from a future time, mortal... Such wonders I have seen...

Oops! My mistake! Firefox 3.04, to be precise. Recent upgrade. Saw the "4" and misread it. :o

and JPEGs don't support transparency.

That's right... I was most taken aback!

Check your css and make sure that isn't effecting anything.

Nuthin' in there to suggest transparency has been invoked... Yes, my graphic was misplaced at first; hanging over the top of other elements. Not absolute positioned and no z-index coded in, either, so very strange indeed.

The file extension definitely isn't PNG. It's a background image, which is a JPEG.

The only explanation I can think of, is that somehow, the future is leaking into our present, through a dimensional wormhole, accidentally created in the LHC...

What a boggle, eh?
http://i183.photobucket.com/albums/x103/Doctor_Varney/signature.gif

You missed Aero's comment?