I've just updated my Snow Leopard (non-server) install to Lion Server, and now when I try to go into the server app's "web" configuration section, I just get "error reading settings". I assume that this is because I'd manually edited my httpd.conf to allow PHP access (as well as PHP mySQL support) in my old Snow Leopard client install. Is there a way to get back to a defaul Lion web server configuration (other than a full re-install)?
You could try to restore the default config file.
make sure server.app is closed then
sudo mv httpd.conf.default httpd.conf
sudo apachectl graceful
let me know if that work