just a recommendation. If you are planning on running the web server on the 400MHz 128 MB of ram, it should work just fine, but install as a text install only. If you install X-windows, you will find that most of the resources will be eaten by the GUI.
Also, once up and running, consider something like webmin which uses the web server to allow you to administer the server from a web interface (kind of like a GUI but without requiring the extensive overhead on the server pc).
Also, eliminating the packages that normally accompany a GUI install will give you quite a bit more disk space to server up web pages. It's a fun place to begin.