Thanks Bob.
What he is saying on that Very Complicated web page is ..
The Professor gif, the blank blackboard, and the dust image under it, are the only real downloadable images.

The four dusty blackboard images below them are not real.
They are being created on the page by all of the CSS code you see around them on the page.

Even the Dusty Blackboard Banner below the upper professor gif, and the transparity of the dust on blackboards 3 and 4 is being done by the CSS codes you see on the page. 😊