Added discussion on setting up a local test web server

Author: clyne

README.md

@@ -27,15 +27,27 @@ conda env create -f ../ci/environment.yml
 conda activate pythia
 ```
 
-You can then build the site:
+You can then build the site with:
 
 ```
 make html
 ```
-and view the built site in your web browser with:
+
+After building the site it may be possible to preview the portal in your web browser by simply opening the `index.html` file:
 
 ```
 open _build/html/index.html
 ```
 
+However, many of the links will not work. For all of the links found in the portal to work properly, you'll need to set up a local testing server. This can be done with Python's http.server by running the following command from within the `content` directory:
+
+```
+python -m http.server --directory _build/html/
+```
+
+and then pointing your browser at the URL: `localhost:8000`
+
+More information on setting up a local test server is available from [here](https://developer.mozilla.org/en-US/docs/Learn/Common_questions/set_up_a_local_testing_server)
+
+
 You can find more details in the [Contributor's Guide](https://projectpythia.org/pages/contributing.html).