Do I need to open source a commercial website that uses GPL components?

Question

MODX

This may sound like a dumb question, but I've looked through a bunch of articles and questions about the GPL and still don't get it about websites. Let's say I have a commercial website - message board - on MODx. Since MODX is licensed under the GPL (as are the modules it uses), do I have to publish the source of the website (meaning the back end)? The same question regarding the ExtJS framework - can I use it in my frontend project without disclosing the server sources.