minor formatting

Author: jmckenna

en/cgi/openlayers.txt

@@ -110,7 +110,9 @@ If you don't have a live MapServer install to play with, you try the
 Customizing settings
 ~~~~~~~~~~~~~~~~~~~~
 
-* environment variables::
+The viewer relies on two external files - a JavaScript file and a CSS file. By default these are loaded
+from ``https://mapserver.org/lib/``, however you can use your own copies of these files if external network access
+is restricted by setting the following two :ref:`environment_variables`:
 
 * ``MS_OPENLAYERS_JS_URL`` - the URL to the OpenLayers JavaScript library. 
 * ``MS_OPENLAYERS_CSS_URL`` - the URL to the OpenLayers CSS file used for styling. 
@@ -130,7 +132,10 @@ If you aren't providing your own OpenLayers library through ``MS_OPENLAYERS_JS_U
 ``MS_OPENLAYERS_CSS_URL``, MapServer will point to hard-coded filepaths at `mapserver.org/lib` to find the OpenLayers 
 library, referred to in `maptemplate.c <https://github.com/MapServer/MapServer/blob/main/src/maptemplate.c#L54>`_.
 
-The contents on that `lib` folder is stored in the MapServer documentation repository, 
-in the [/extra](https://github.com/MapServer/MapServer-documentation/tree/main/extra) folder.
+This version of OpenLayers is a cut-down version that only contains the classes needed for the
+MapServer viewer. The ``ol-mapserver.js`` file is ~200 KB compared to the full library which is ~ 840 KB.
+
+The contents of that `lib` folder is stored in the MapServer documentation repository, 
+in the `/extra <https://github.com/MapServer/MapServer-documentation/tree/main/extra>`_ folder.
 You are warmly encouraged to contribute to upgrading the OpenLayers library, at any time (maybe start 
-with creating a new [Pull Request](https://github.com/MapServer/MapServer-documentation/pulls) there.
+with creating a new `Pull Request <https://github.com/MapServer/MapServer-documentation/pulls>`_ there).