Why does CSS2.1 define overflow values other than “visible” to establish a new block formatting context?
I asked about this on the mailing list on your behalf; the thread can be found here. In summary, this has to do with scrolling content for the most part: Fundamentally, because if the spec didn’t say this, then having floats intersect with something that’s scrollable would require the browser to rewrap (around intruding floats) … Read more