I think this has all to do with my curiosity.

Every image placed on a RSD v1.5 page gets the following bit of code:
<img src="nodata...image/gif;base64,R0lGODlhAQABAIAAAAAAAP///yH5BAEAAAAALAAAAAABAAEAAAIBRAA7">

Can someone please explain the reason, and please ignore my ignorance if I ask what the purpose of this is.

I asked this in my support room, and received the following explanation.

"Some older browsers do not support the <picture> element. We use javascript as fallback, this fetches the default image for these browsers. Now, if an old browser is used AND javascript is disabled, an error could occur. The code you see there is to prevent showing a broken image under these circumstances. Other workarounds would cause modern browsers to fetching 2 images when javascript is disabled. Finally this code solves validation notices related to missing scr attributes."

Frank

Thanks for providing the answer, Frank. I had been wondering about the same.

Thanks Frank. Now we know. Good reason not to delete as I was tempted to do.

Wow - the CC folks don't miss a trick! Another reason why I'm always very impressed with their software.