here is an easy way to find out:

1) right click go to properties of the image (example: https://o.view.usg.edu/images/logo.gif)

2) now that you got the name of the image right click on the page and go to view source, ctrl + f and type in the name of the image

3) code should look something like this:

<a href=""><img src="https://o.view.usg.edu/images/logo.gif" border="0" /></a>