fix doc

docs/scripts/heading-anchors.md

@@ -1,12 +1,12 @@
 # Heading anchors
 
-This script is part of `main.js`/`main.min.js`. To help linking to specific parts of pages, this script automatically creates and appends a visible anchor link to the end of any H2-H6 heading within the `<main>` element, with the following exclusions:
+This script is part of `main.js`/`main.min.js`. To help linking to specific parts of pages, this script automatically creates and appends a visible anchor link to the end of any H2-H6 heading that have an `id` attribute within the `<main>` element, with the following exclusions:
 
 - where the heading is a child of a `<nav>` element
 - where the heading carries the attribute `data-anchor="no"`, the `hidden` attribute or the `.visuallyhidden` class
 - where a heading has an ancestor carrying the attribute `data-anchor="no"`, the `hidden` attribute or the `.visuallyhidden` class
 
-If a heading already has an `id` attribute, this is used when creating the `href` for the `<a>`. Otherwise, the script parses the text content of the heading to create both the heading `id` and the anchor `href`.
+The `id` attribute is used when creating the `href` for the `<a>`.
 
 To override the default behaviour of the script and prevent the addition of anchor links to headings, modify the HTML markup to apply the `data-anchor="no"` attribute to an individual heading (or to a parent container, if targeting a group of headings).
 
@@ -18,4 +18,4 @@ The `data-anchor="no"` attribute has been added directly to the markup to overri
 - [collapsible containers](../components/collapsible-containers.md)
 - [evangelists](../components/evangelists.md)
 - [group list](../components/group-list.md)
-- [notes](../components/notes.md)
+- [notes](../components/notes.md)