Often the content is available without masking for a very short time so scrapers can access them or similar tricks to allow them access immediately after posting. But that requires that you hit the server immediately after the story is posted and there is no masking at all usually in those cases. That's how things like archive.is get a copy for example. But none of that is client/browser side anymore, at least on the major sites. Otherwise it's easy to defeat if the content is already provided to the browser and just masked with JavaScript or something that runs locally and can be blocked.