You'd probably be better off using Rails or Django right now. Writing a web framework in Lisp is an order of magnitude harder than just using a battle tested one.
I think most people mean something more like Uncommonweb or KPAX. I built a fairly sophisticated application for a client using TBNL (now Hunchentoot), CL-WHO and CLSQL.
Building a web application doesn't require a framework; it does require a set of libraries to handle talking over http, generating HTML and often talking to a database. Since most frameworks include these, some people may confuse the two. A framework is really just a half-done bottom-up application, which is pretty useful when it matches the kind of application you're building and pretty useless otherwise.
But the idea is that what you get out of lisp is an order of magnitude more power than other battle-tested ones, right? I ask this in seriousness, not to provoke a flame war.
[edit: I'm not entirely sure what people mean when they say web framework, so apologies if Hunchentoot wasn't what you meant.]