diff --git a/changelogs/internal/newsfragments/1880.clarification b/changelogs/internal/newsfragments/1880.clarification
new file mode 100644
index 00000000..56090e20
--- /dev/null
+++ b/changelogs/internal/newsfragments/1880.clarification
@@ -0,0 +1 @@
+Fix validation errors in generated HTML.
diff --git a/content/client-server-api/modules/push.md b/content/client-server-api/modules/push.md
index c674bac9..2d828a01 100644
--- a/content/client-server-api/modules/push.md
+++ b/content/client-server-api/modules/push.md
@@ -521,7 +521,7 @@ Definition:
 }
 ```
 
-<a id="_m_rule_is_user_mention"/> **`.m.rule.is_user_mention`**
+<a id="_m_rule_is_user_mention"></a> **`.m.rule.is_user_mention`**
 
 {{< added-in v="1.7" >}}
 
@@ -555,7 +555,7 @@ Definition:
 }
 ```
 
-<a id="_m_rule_contains_display_name"/> **`.m.rule.contains_display_name`**
+<a id="_m_rule_contains_display_name"></a> **`.m.rule.contains_display_name`**
 
 {{% changed-in v="1.7" %}}
 
@@ -590,7 +590,7 @@ Definition:
 }
 ```
 
-<a id="_m_rule_is_room_mention"/> **`.m.rule.is_room_mention`**
+<a id="_m_rule_is_room_mention"></a> **`.m.rule.is_room_mention`**
 
 {{< added-in v="1.7" >}}
 
@@ -624,7 +624,7 @@ Definition:
 }
 ```
 
-<a id="_m_rule_roomnotif"/> **`.m.rule.roomnotif`**
+<a id="_m_rule_roomnotif"></a> **`.m.rule.roomnotif`**
 
 {{% changed-in v="1.7" %}}
 
@@ -662,7 +662,7 @@ Definition:
 }
 ```
 
-**<a name="mruletombstone"></a>`.m.rule.tombstone`**
+**<a id="mruletombstone"></a>`.m.rule.tombstone`**
 
 Matches any state event whose type is `m.room.tombstone`. This is
 intended to notify users of a room when it is upgraded, similar to what
@@ -696,7 +696,7 @@ Definition:
 }
 ```
 
-**<a name="mrulereaction"></a>`.m.rule.reaction`**
+**<a id="mrulereaction"></a>`.m.rule.reaction`**
 
 {{% added-in v="1.7" %}}
 
@@ -776,7 +776,7 @@ Definition:
 
 ##### Default Content Rules
 
-<a id="_m_rule_contains_user_name"/> **`.m.rule.contains_user_name`**
+<a id="_m_rule_contains_user_name"></a> **`.m.rule.contains_user_name`**
 
 {{% changed-in v="1.7" %}}
 
diff --git a/layouts/partials/events/render-event.html b/layouts/partials/events/render-event.html
index 71ba60bd..154e51bf 100644
--- a/layouts/partials/events/render-event.html
+++ b/layouts/partials/events/render-event.html
@@ -101,4 +101,6 @@
     {{ end }}
 {{ end }}
 
+</details>
+
 </section>
diff --git a/layouts/partials/openapi/render-content-type.html b/layouts/partials/openapi/render-content-type.html
index 036522de..96033e16 100644
--- a/layouts/partials/openapi/render-content-type.html
+++ b/layouts/partials/openapi/render-content-type.html
@@ -16,8 +16,10 @@
 
 <table class="content-type-table">
  <thead>
-  <th class="col-name">Content-Type</th>
-  <th class="col-description">Description</th>
+  <tr>
+    <th class="col-name">Content-Type</th>
+    <th class="col-description">Description</th>
+  </tr>
  </thead>
  {{ range $idx, $content_type := $content_types }}
  <tr>
diff --git a/layouts/partials/openapi/render-object-table.html b/layouts/partials/openapi/render-object-table.html
index d2b09acb..3fd49f0b 100644
--- a/layouts/partials/openapi/render-object-table.html
+++ b/layouts/partials/openapi/render-object-table.html
@@ -31,9 +31,11 @@
  <caption>{{ . }}</caption>
  {{ end }}
  <thead>
-  <th class="col-name">Name</th>
-  <th class="col-type">Type</th>
-  <th class="col-description">Description</th>
+  <tr>
+    <th class="col-name">Name</th>
+    <th class="col-type">Type</th>
+    <th class="col-description">Description</th>
+  </tr>
  </thead>
 
     {{ range $property_name, $property := $properties }}
@@ -68,7 +70,7 @@
     {{ if reflect.IsMap .additionalProperties }}
 
  <tr>
-  <td>&lt;Other properties&gt;</code></td>
+  <td>&lt;Other properties&gt;</td>
   <td><code>{{ partial "partials/property-type" .additionalProperties | safeHTML }}</code></td>
   <td>{{ partial "partials/property-description" (dict "property" .additionalProperties) }}</td>
  </tr>
@@ -90,8 +92,10 @@ resolve-additional-types.)
  <caption>{{ . }}</caption>
  {{ end }}
  <thead>
-  <th class="col-type">Type</th>
-  <th class="col-description">Description</th>
+  <tr>
+    <th class="col-type">Type</th>
+    <th class="col-description">Description</th>
+  </tr>
  </thead>
 
  {{ $property := . }}
diff --git a/layouts/partials/openapi/render-operation.html b/layouts/partials/openapi/render-operation.html
index 8c6fce0e..ef525353 100644
--- a/layouts/partials/openapi/render-operation.html
+++ b/layouts/partials/openapi/render-operation.html
@@ -46,7 +46,7 @@
   {{ partial "changed-in" (dict "changes_dict" (index $operation_data "x-changedInMatrixVersion")) }}
 {{ end -}}
 
-<p>{{ $operation_data.description | markdownify }}</p>
+{{ $operation_data.description | page.RenderString (dict "display" "block") }}
 
 
 <table class="basic-info">
diff --git a/layouts/partials/openapi/render-responses.html b/layouts/partials/openapi/render-responses.html
index 0ffc4884..80dcb582 100644
--- a/layouts/partials/openapi/render-responses.html
+++ b/layouts/partials/openapi/render-responses.html
@@ -20,8 +20,10 @@
 
 <table class="response-table">
  <thead>
-  <th class="col-status">Status</th>
-  <th class="col-status-description">Description</th>
+  <tr>
+    <th class="col-status">Status</th>
+    <th class="col-status-description">Description</th>
+  </tr>
  </thead>
 
 {{ range $code, $response := $responses }}
diff --git a/layouts/shortcodes/definition.html b/layouts/shortcodes/definition.html
index a1f0904e..f5d50e75 100644
--- a/layouts/shortcodes/definition.html
+++ b/layouts/shortcodes/definition.html
@@ -66,4 +66,6 @@
 {{ jsonify (dict "indent" "  ") $example }}
 ```
 
+</details>
+
 </section>