Update navigation-structure.md

Adjusted the documentation to explain how mixtures of numbers and strings are treated by `nav_order`.

docs/navigation-structure.md

@@ -25,7 +25,7 @@ By default, all pages will appear as top level pages in the main nav unless a pa
 
 ## Ordering pages
 
-To specify a page order, use the `nav_order` parameter in your pages' YAML front matter.
+To specify a page order, you can use the `nav_order` parameter in your pages' YAML front matter.
 
 #### Example
 {: .no_toc }
@@ -38,12 +38,13 @@ nav_order: 4
 ---
 ```
 
-The specified `nav_order` parameters on a site should be all integers or all strings.
-Pages without a `nav_order` parameter are ordered alphabetically by their `title`,
-and appear after the explicitly-ordered pages at each level.
-By default, all Capital letters are sorted before all lowercase letters;
-adding `nav_sort: case_insensitive` in the configuration file ignores case
-when sorting strings (but also sorts numbers lexicographically: `10` comes before `1`).
+The parameter values determine the order of the top-level pages, and of child pages with the same parent. You can reuse the same parameter values (e.g., integers starting from 1) for the child pages of different parents.
+
+The parameter values can be numbers (integers, floats) and/or strings. When you omit `nav_order` parameters, they default to the titles of the pages, which are ordered alphabetically. Pages with numerical `nav_order` parameters always come before those with strings or default `nav_order` parameters. If you want to make the page order independent of the page titles, you can set explicit `nav_order` parameters on all pages.
+
+By default, all Capital letters come before all lowercase letters; you can add `nav_sort: case_insensitive` in the configuration file to ignore the case). Enclosing strings in quotation marks is optional.
+
+> *Note for users of previous versions:* `nav_sort: case_insensitive` previously affected the ordering of numerical `nav_order` parameters: e.g., `10` came before `2`. Also, all pages with explicit `nav_order` parameters previously came before all pages with default parameters.
 
 ---
 
@@ -62,6 +63,8 @@ nav_exclude: true
 ---
 ```
 
+Pages with no `title` are automatically excluded from the navigation.
+
 ---
 
 ## Pages with children