Where are broken CSS images used?
Broken images are detected when a style sheet has undergone many changes, for instance after a migration of a website or an upgrade of the website design. The first indication could be that broken images (red crosses) appear on the screen when the website is loading. Another indication is that the 404 not found log of the web server becomes contaminated with links to images that no longer exist.
If there's any suspicion of broken images on the website, it can be an incredibly time-consuming job to check every single link in the style sheet to images for broken images. It's therefore probably more effective to have this check done automatically by means of a tool that checks realtime whether all images in a style sheet can still be loaded.