HTML framesets have some good uses, such as including third-party content. They also have misuses, such as disguising third-party involvement.
Recently I needed to set up domain forwarding for a subdomain registered with Godaddy. (The choice of registrar wasn’t my fault.) A couple of options were available, including one that claimed to guarantee that the subdomain would persist through navigation in the address bar. That sounded like a good thing, so I picked it.
At first it seemed to work fine; but when I tried to use the URL of an image on the site, there were weird errors. I soon found out what was going on: Godaddy was wrapping every page referenced by the subdomain in a frameset! This looks like a duck and clicks like a duck, but it isn’t one, and anything that tries to treat HTML as a JPEG file isn’t going to work very well.
Stack Overflow has several reports of people being bitten by this:
Frame wrapping is a good-enough solution for some cases, but when you aren’t told it’s happening, that’s a seriously wrong way to do it. It’s also a security concern, since your domain points at an IP address that you don’t control, and only indirectly at your own site.
This is a blog on file formats, not on irresponsible domain registrars, so the moral here is to realize that framesets aren’t a completely transparent way to provide third-party content. It’s fine to use them, but only if you’re aware that the frameset host and the frame provider are active partners.