How Identify 404 error in Webview

Hello guys can anyone suggest to me, how to identify the 404 error in webview. If anyone fixes this challenge please share the block.
Actually, I have loaded some images in webview so if the image is not available then it should show another one. So I need to identify the 404.

how do you load the images? any screenshot?
you might want to check the url of the 404 page using the current Url property?

I think there was an event to detect errors in webview.