I'll answer your question about sigs this way so you don't have to dig through the closed reports~
I'm on Chrome, so things might be different for you.
If you right click on the gif in question, you'll get the usual menu, and go down to "Inspect Element". When you do, a separate window at the bottom of the screen will appear, and you'll need to go through the mess of code to find the actual gif. (The CSS turns the image into a not-image, so this is the only way to get the properties.) Once you find the actual gif, it will pop up on the side with the dimensions and filesize, letting you know all you need to know.
The more you know! ★