diff --git a/html/browsers/browsing-the-web/navigating-across-documents/010-form-action-javascript-url-aborted-by-navigation.html b/html/browsers/browsing-the-web/navigating-across-documents/010-form-action-javascript-url-aborted-by-navigation.html
new file mode 100644
index 000000000000000..ef62455b635f7df
--- /dev/null
+++ b/html/browsers/browsing-the-web/navigating-across-documents/010-form-action-javascript-url-aborted-by-navigation.html
@@ -0,0 +1,56 @@
+<!doctype html>
+<link rel="help" href="https://html.spec.whatwg.org/multipage/browsing-the-web.html#navigating-across-documents">
+<link rel="help" href="https://html.spec.whatwg.org/multipage/browsing-the-web.html#javascript-protocol">
+<link rel="help" href="https://html.spec.whatwg.org/multipage/form-control-infrastructure.html#concept-form-submit">
+<link rel="help" href="https://html.spec.whatwg.org/multipage/form-control-infrastructure.html#submit-get-action">
+<link rel="help" href="https://html.spec.whatwg.org/multipage/form-control-infrastructure.html#plan-to-navigate">
+<link rel="help" href="https://html.spec.whatwg.org/multipage/form-control-infrastructure.html#planned-navigation">
+<link rel="help" href="https://html.spec.whatwg.org/multipage/webappapis.html#queue-a-task">
+<link rel="help" href="https://html.spec.whatwg.org/multipage/webappapis.html#dom-manipulation-task-source">
+<title>Link with onclick form submit to navigate "javascript: url" in nested browsing context, is aborted by href navigation</title>
+<script src="/resources/testharness.js"></script>
+<script src="/resources/testharnessreport.js"></script>
+<div id="log"></div>
+<iframe id="test" name="test"></iframe>
+<!-- Everything seen in the action="" is necessary to prevent a blank page in Chrome -->
+<form target="test" action="javascript:parent.postMessage(location.href, '*');"></form>
+<a target="test" onclick="document.forms[0].submit();reports.push('onclick');" href="href.html">Test</a>
+<script>
+var test = async_test();
+var reports = [];
+
+window.onmessage = test.step_func(function(e) {
+  reports.push(e.data);
+  // "href" is expected last, if this is not received last or
+  // not received at all, the test must fail.
+  if (e.data === "href") {
+    assert_equals(reports[0], "click");
+    assert_equals(reports[1], "onclick");
+    assert_equals(reports[2], "href");
+    assert_equals(reports.length, 3);
+  } else {
+
+
+  }
+  test.done();
+});
+
+test.step(function() {
+  reports.push("click");
+  document.querySelector("a").click();
+});
+</script>
+
+<!--
+1. This test creates an iframe, a form with `action="javascript:...", and
+    an anchor with both an `onclick` and `href`.
+2. The test "clicks" the anchor, triggering the `onclick` handler operation,
+    which will attempt to submit the form, which targets the iframe.
+3. The form action "javascript: url" navigation is queued in a task.
+4. Navigating the iframe to the anchor's `href` must abort the iframe
+    "javascript: url" navigation.
+5. If the semantics are implemented correctly, reports will be
+    ["click", "onclick", "href"].
+    (There will be no report from the "javascript: url" code, because it
+    is aborted by the navigation to "href.html")
+-->
diff --git a/html/browsers/browsing-the-web/navigating-across-documents/010.html b/html/browsers/browsing-the-web/navigating-across-documents/010.html
deleted file mode 100644
index 3917cd16e5578d5..000000000000000
--- a/html/browsers/browsing-the-web/navigating-across-documents/010.html
+++ /dev/null
@@ -1,17 +0,0 @@
-<!doctype html>
-<title>Link with onclick form submit to javascript url with delayed document.write and href navigation </title>
-<script src="/resources/testharness.js"></script>
-<script src="/resources/testharnessreport.js"></script>
-<div id="log"></div>
-<iframe id="test" name="test"></iframe>
-<form target="test" action="javascript:(function() {var x = new XMLHttpRequest(); x.open('GET', 'blank.html?pipe=trickle(d2)', false); x.send(); document.write('<script>parent.postMessage(&quot;write&quot;, &quot;*&quot;)</script>'); return '<script>parent.postMessage(&quot;click&quot;, &quot;*&quot;)</script>'})()"></form>
-<a target="test" onclick="document.forms[0].submit()" href="href.html">Test</a>
-<script>
-var t = async_test(undefined, {timeout:4000});
-t.step(function() {document.getElementsByTagName("a")[0].click()});
-onmessage = t.step_func(
-  function(e) {
-    assert_equals(e.data, "href");
-    t.done();
-  });
-</script>
diff --git a/html/browsers/browsing-the-web/navigating-across-documents/011.html b/html/browsers/browsing-the-web/navigating-across-documents/011.html
index fe6b8dbc3560fba..27d0f4d33db25eb 100644
--- a/html/browsers/browsing-the-web/navigating-across-documents/011.html
+++ b/html/browsers/browsing-the-web/navigating-across-documents/011.html
@@ -1,21 +1,39 @@
 <!doctype html>
-<title>Link with onclick navigation to javascript url with document.write and href navigation </title>
+<link rel="help" href="https://html.spec.whatwg.org/multipage/browsing-the-web.html#navigating-across-documents">
+<title>Link with onclick that does not attempt to navigate and href navigation</title>
 <script src="/resources/testharness.js"></script>
 <script src="/resources/testharnessreport.js"></script>
 <div id="log"></div>
 <iframe id="test" name="test"></iframe>
-<a target="test" onclick="javascript:(function() {document.write('<script>parent.postMessage(&quot;write&quot;, &quot;*&quot;)</script>'); return '<script>parent.postMessage(&quot;click&quot;, &quot;*&quot;)</script>'})()" href="href.html">Test</a>
+<a target="test" onclick="reports.push('onclick');" href="href.html">Test</a>
 <script>
-var t = async_test();
-var events = [];
-t.step(function() {
-  document.getElementsByTagName("a")[0].click()});
-onmessage = t.step_func(
-  function(e) {
-    events.push(e.data);
-    if (events.length === 2) {
-      assert_array_equals(events, ["write", "href"]);
-      t.done();
-    }
-  });
+var test = async_test();
+var reports = [];
+test.step(function() {
+  reports.push("click");
+  document.querySelector("a").click();
+});
+window.onmessage = test.step_func(function(e) {
+  reports.push(e.data);
+
+  // "href" is expected last, if this is not received last or
+  // not received at all, the test must fail.
+  if (e.data === "href") {
+    assert_equals(reports[0], "click");
+    assert_equals(reports[1], "onclick");
+    assert_equals(reports[2], "href");
+    assert_equals(reports.length, 3);
+    test.done();
+  }
+});
 </script>
+
+<!--
+1. This test creates an iframe and an anchor with both an `onclick` and `href`.
+2. The test "clicks" the anchor, triggering the `onclick` handler operation,
+    which adds a message to the reports array.
+3. Navigate the iframe to the anchor's `href`.
+4. If the semantics are implemented correctly, reports will be
+    ["click", "onclick", "href"].
+
+-->
diff --git a/html/browsers/browsing-the-web/navigating-across-documents/012-async-timeout.html b/html/browsers/browsing-the-web/navigating-across-documents/012-async-timeout.html
new file mode 100644
index 000000000000000..c411b7aee269ad1
--- /dev/null
+++ b/html/browsers/browsing-the-web/navigating-across-documents/012-async-timeout.html
@@ -0,0 +1,44 @@
+<!doctype html>
+<link rel="help" href="https://html.spec.whatwg.org/multipage/browsing-the-web.html#navigating-across-documents">
+<title>Link with onclick, which executes a handler containing a timeout, that then navigates the iframe, and returns true.</title>
+<script src="/resources/testharness.js"></script>
+<script src="/resources/testharnessreport.js"></script>
+<div id="log"></div>
+<iframe id="test" name="test"></iframe>
+<a target="test" onclick="(function(){setTimeout(()=>document.querySelector('iframe').src='call-parent-postmessage.html', 500);reports.push('onclick');})()" href="href.html">Test</a>
+<script>
+var test = async_test();
+var reports = [];
+
+window.onmessage = test.step_func(function(e) {
+  reports.push(e.data);
+
+  // "call-parent-postmessage" is expected last, if this is not received last or
+  // not received at all, the test must fail.
+  if (e.data === "call-parent-postmessage") {
+    assert_equals(reports[0], "click", reports);
+    assert_equals(reports[1], "onclick", reports);
+    assert_equals(reports[2], "href", reports);
+    assert_equals(reports[3], "call-parent-postmessage");
+    assert_equals(reports.length, 4);
+    test.done();
+  }
+});
+
+test.step(function() {
+  reports.push("click");
+  document.querySelector("a").click();
+});
+</script>
+
+<!--
+1. This test creates an iframe and an anchor with both an `onclick` and `href`.
+2. The test "clicks" the anchor, triggering the `onclick` handler operation,
+    which will attempt to navigate the iframe after an async timeout.
+3. Navigating the iframe to the anchor's `href` will complete successfully,
+    then the queued timeout will execute and the next navigation will occur
+    and also complete successfully.
+4. If the semantics are implemented correctly, reports will be
+    ["click", "onclick", "href", "call-parent-postmessage"].
+
+-->
diff --git a/html/browsers/browsing-the-web/navigating-across-documents/012-blocking-then-async-postmessage.html b/html/browsers/browsing-the-web/navigating-across-documents/012-blocking-then-async-postmessage.html
new file mode 100644
index 000000000000000..c4bffde7d005174
--- /dev/null
+++ b/html/browsers/browsing-the-web/navigating-across-documents/012-blocking-then-async-postmessage.html
@@ -0,0 +1,46 @@
+<!doctype html>
+<link rel="help" href="https://html.spec.whatwg.org/multipage/browsing-the-web.html#navigating-across-documents">
+<title>Link with onclick, which executes a handler containing a 100ms blocking operation, then iframe document.write, then returns true.</title>
+<script src="/resources/testharness.js"></script>
+<script src="/resources/testharnessreport.js"></script>
+<div id="log"></div>
+<iframe id="test" name="test"></iframe>
+ <a target="test" onclick="(function() {((e,n)=>{var a=e();while(e()<a+n);})(Date.now,100); document.querySelector('iframe').contentDocument.write('<script>parent.postMessage(&quot;write-post-message&quot;, &quot;*&quot;)</script>');reports.push('onclick');return true;})()" href="href.html">Test</a>
+
+<script>
+var test = async_test();
+var reports = [];
+var iframe = document.querySelector('iframe');
+
+window.onmessage = test.step_func(function(e) {
+  reports.push(e.data);
+
+  // "href" is expected last, if this is not received last or
+  // not received at all, the test must fail.
+  if (e.data === "href") {
+    assert_equals(reports[0], "click");
+    assert_equals(reports[1], "onclick");
+    // This comes after "onclick" because it's
+    // sent via postMessage
+    assert_equals(reports[2], "write-post-message");
+    assert_equals(reports[3], "href");
+    assert_equals(reports.length, 4);
+    test.done();
+  }
+});
+
+test.step(function() {
+  reports.push("click");
+  document.querySelector("a").click();
+});
+</script>
+
+<!--
+1. This test creates an iframe and an anchor with both an `onclick` and `href`.
+2. The test "clicks" the anchor, triggering the `onclick` handler operation,
+    which will document.write a script to the iframe which sends a message "write".
+3. Navigate the iframe to the anchor's `href`
+4. If the semantics are implemented correctly, reports will be
+    ["click", "onclick", "write-post-message", "href"]
+
+-->
diff --git a/html/browsers/browsing-the-web/navigating-across-documents/012.html b/html/browsers/browsing-the-web/navigating-across-documents/012.html
deleted file mode 100644
index be8f2feba8244a5..000000000000000
--- a/html/browsers/browsing-the-web/navigating-across-documents/012.html
+++ /dev/null
@@ -1,20 +0,0 @@
-<!doctype html>
-<title>Link with onclick navigation to javascript url with delayed document.write and href navigation </title>
-<script src="/resources/testharness.js"></script>
-<script src="/resources/testharnessreport.js"></script>
-<div id="log"></div>
-<iframe id="test" name="test"></iframe>
-<!-- XXX: What is this test trying to do?  It's navigating the subframe, but
-     doing a write() to _this_ document, and the "javascript:" in there is
-     completely a red herring: it's a label, not a protocol.  There is no
-     javascript url involved here, unlike what the title claims! -->
-<a target="test" onclick="javascript:(function() {var x = new XMLHttpRequest(); x.open('GET', 'blank.html?pipe=trickle(d2)', false); x.send(); document.write('write<script>parent.postMessage(&quot;write&quot;, &quot;*&quot;)</script>'); return '<script>parent.postMessage(&quot;click&quot;, &quot;*&quot;)</script>'})()" href="href.html">Test</a>
-<script>
-var t = async_test(undefined, {timeout:4000});
-t.step(function() {document.getElementsByTagName("a")[0].click()});
-onmessage = t.step_func(
-  function(e) {
-    assert_equals(e.data, "href");
-    t.done();
-  });
-</script>
diff --git a/html/browsers/browsing-the-web/navigating-across-documents/013.html b/html/browsers/browsing-the-web/navigating-across-documents/013.html
index 69ce7bc6168a9af..7f4ccd71b7fbe71 100644
--- a/html/browsers/browsing-the-web/navigating-across-documents/013.html
+++ b/html/browsers/browsing-the-web/navigating-across-documents/013.html
@@ -1,20 +1,46 @@
 <!doctype html>
-<title>Link with onclick navigation to javascript url with delayed document.write and href navigation </title>
+<link rel="help" href="https://html.spec.whatwg.org/multipage/browsing-the-web.html#navigating-across-documents">
+<link rel="help" href="https://html.spec.whatwg.org/multipage/browsing-the-web.html#javascript-protocol">
+<link rel="help" href="https://html.spec.whatwg.org/multipage/text-level-semantics.html#the-a-element">
+<link rel="help" href="https://html.spec.whatwg.org/multipage/webappapis.html#the-event-handler-processing-algorithm">
+<link rel="help" href="https://html.spec.whatwg.org/multipage/iframe-embed-object.html#the-iframe-element:about:blank">
+<title>Link with href navigation to "javascript: url", order of execution</title>
 <script src="/resources/testharness.js"></script>
 <script src="/resources/testharnessreport.js"></script>
 <div id="log"></div>
 <iframe id="test" name="test"></iframe>
-<a target="test" href="javascript:parent.events.push('javascript');">Test</a>
+<a target="test" href="javascript:parent.postMessage(location.href, '*');">Test</a>
 <script>
-var t = async_test(undefined, {timeout:4000});
-var events = [];
-t.step(function() {
-  document.getElementsByTagName("a")[0].click();
-  events.push('after script');
+var test = async_test();
+var reports = [];
+
+window.onmessage = test.step_func(function(e) {
+  reports.push(e.data);
+  // "about:blank" is expected last, if this is not received last or
+  // not received at all, the test must fail.
+  if (e.data === "about:blank") {
+    assert_equals(reports[0], "click");
+    assert_equals(reports[1], "about:blank");
+    assert_equals(reports.length, 2);
+  } else {
+    throw new Error("'javascript: url' code is expected to run asynchronously and in the target nested browsing context");
+  }
+  test.done();
 });
-onload = t.step_func(function() {
-  // javascript: executions are async.
-  assert_array_equals(events, ['after script', 'javascript']);
-  t.done();
+
+test.step(function() {
+  reports.push("click");
+  document.querySelector("a").click();
 });
 </script>
+
+<!--
+1. This test creates an anchor with an href containing a "javascript: url".
+2. The test "clicks" the anchor, triggering the "javascript: url" href navigation,
+    which must be evaluated and executed asynchronously.
+3. location.href is used to prove that the "javascript: url"'s contents
+    are executed in the iframe.
+4. If the semantics are implemented correctly, reports will be
+    ["click", "about:blank"]
+
+-->
diff --git a/html/browsers/browsing-the-web/navigating-across-documents/014.html b/html/browsers/browsing-the-web/navigating-across-documents/014.html
index 605e181858d4c70..fdf4d6e48de5ae3 100644
--- a/html/browsers/browsing-the-web/navigating-across-documents/014.html
+++ b/html/browsers/browsing-the-web/navigating-across-documents/014.html
@@ -1,21 +1,55 @@
 <!doctype html>
-<title> Link with javascript onclick form submission script order </title>
+<link rel="help" href="https://html.spec.whatwg.org/multipage/browsing-the-web.html#navigating-across-documents">
+<link rel="help" href="https://html.spec.whatwg.org/multipage/browsing-the-web.html#javascript-protocol">
+<link rel="help" href="https://html.spec.whatwg.org/multipage/text-level-semantics.html#the-a-element">
+<link rel="help" href="https://html.spec.whatwg.org/multipage/webappapis.html#the-event-handler-processing-algorithm">
+<link rel="help" href="https://html.spec.whatwg.org/multipage/form-control-infrastructure.html#concept-form-submit">
+<link rel="help" href="https://html.spec.whatwg.org/multipage/form-control-infrastructure.html#submit-get-action">
+<link rel="help" href="https://html.spec.whatwg.org/multipage/form-control-infrastructure.html#plan-to-navigate">
+<link rel="help" href="https://html.spec.whatwg.org/multipage/form-control-infrastructure.html#planned-navigation">
+<link rel="help" href="https://html.spec.whatwg.org/multipage/iframe-embed-object.html#the-iframe-element:about:blank">
+<title>Link with onclick form submit to "javascript: url", order of execution</title>
 <script src="/resources/testharness.js"></script>
 <script src="/resources/testharnessreport.js"></script>
 <div id="log"></div>
 <iframe id="test" name="test"></iframe>
-<form target="test" action="javascript:parent.events.push('submit');"></form>
-<a target="test" onclick="document.forms[0].submit()">Test</a>
+<form target="test" action="javascript:parent.postMessage(location.href, '*');"></form>
+<a target="test" onclick="reports.push('onclick');document.forms[0].submit();">Test</a>
 <script>
-var t = async_test(undefined, {timeout:4000});
-var events = [];
-t.step(function() {
-  document.getElementsByTagName("a")[0].click();
-  events.push('after script');
+var test = async_test();
+var reports = [];
+
+window.onmessage = test.step_func(function(e) {
+  reports.push(e.data);
+
+  // "about:blank" is expected last, if this is not received last or
+  // not received at all, the test must fail.
+  if (e.data === "about:blank") {
+    assert_equals(reports[0], "click");
+    assert_equals(reports[1], "onclick");
+    assert_equals(reports[2], "about:blank");
+    assert_equals(reports.length, 3);
+  } else {
+    throw new Error("'javascript: url' code is expected to run asynchronously and in the target nested browsing context");
+  }
+  test.done();
 });
-onload = t.step_func(function() {
-  // javascript: executions are async.
-  assert_array_equals(events, ['after script', 'submit']);
-  t.done();
+
+test.step(function() {
+  reports.push("click");
+  document.querySelector("a").click();
 });
 </script>
+
+<!--
+1. This test creates a form with `target="test" and an anchor with both an
+    onclick and href.
+2. The test clicks the anchor, which will trigger the onclick handler
+    operation, which will attempt to submit the form. The form's `action` is
+    a "javscript: url", which must be evaluated and executed asynchronously.
+3. location.href is used to prove that the "javscript: url"'s contents are
+    executed in the iframe.
+4. If the semantics are implemented correctly, reports will be
+    ["click", "onclick", "about:blank"]
+
+-->
diff --git a/html/browsers/browsing-the-web/navigating-across-documents/015.html b/html/browsers/browsing-the-web/navigating-across-documents/015.html
index eb54622b785ea12..3c7268e4fcaab2b 100644
--- a/html/browsers/browsing-the-web/navigating-across-documents/015.html
+++ b/html/browsers/browsing-the-web/navigating-across-documents/015.html
@@ -1,20 +1,48 @@
 <!doctype html>
-<title> Link with javascript onclick and href script order </title>
+<link rel="help" href="https://html.spec.whatwg.org/multipage/browsing-the-web.html#navigating-across-documents">
+<link rel="help" href="https://html.spec.whatwg.org/multipage/browsing-the-web.html#javascript-protocol">
+<link rel="help" href="https://html.spec.whatwg.org/multipage/text-level-semantics.html#the-a-element">
+<link rel="help" href="https://html.spec.whatwg.org/multipage/webappapis.html#the-event-handler-processing-algorithm">
+<link rel="help" href="https://html.spec.whatwg.org/multipage/iframe-embed-object.html#the-iframe-element:about:blank">
+<title>Link with onclick and href javascript: url, order of execution</title>
 <script src="/resources/testharness.js"></script>
 <script src="/resources/testharnessreport.js"></script>
 <div id="log"></div>
 <iframe id="test" name="test"></iframe>
-<a target="test" onclick="parent.events.push('click');" href="javascript:parent.events.push('href')">Test</a>
+<a target="test" onclick="reports.push('onclick');" href="javascript:parent.postMessage(location.href, '*');">Test</a>
 <script>
-var t = async_test(undefined, {timeout:4000});
-var events = [];
-t.step(function() {
-  document.getElementsByTagName("a")[0].click();
-  events.push('after script');
+var test = async_test();
+var reports = [];
+
+window.onmessage = test.step_func(function(e) {
+  reports.push(e.data);
+
+  // "about:blank" is expected last, if this is not received last or
+  // not received at all, the test must fail.
+  if (e.data === "about:blank") {
+    assert_equals(reports[0], "click");
+    assert_equals(reports[1], "onclick");
+    assert_equals(reports[2], "about:blank");
+    assert_equals(reports.length, 3);
+  } else {
+    throw new Error("'javascript: url' code is expected to run asynchronously and in the target nested browsing context");
+  }
+  test.done();
 });
-onload = t.step_func(function() {
-  // javascript: executions are async.
-  assert_array_equals(events, ['click', 'after script', 'href']);
-  t.done();
+
+test.step(function() {
+  reports.push("click");
+  document.querySelector("a").click();
 });
 </script>
+
+<!--
+1. This test creates an anchor with an href containing a "javascript: url" .
+2. The test clicks the anchor, triggering the "javascript: url" href navigation,
+    which must be evaluated and executed asynchronously.
+3. `location.href` is used to prove that the "javascript: url"'s contents
+    are executed in the iframe.
+4. If the semantics are implemented correctly, reports will be
+    ["click", "onclick", "about:blank"]
+
+-->
diff --git a/html/browsers/browsing-the-web/navigating-across-documents/016-onclick-return-false-no-navigation.html b/html/browsers/browsing-the-web/navigating-across-documents/016-onclick-return-false-no-navigation.html
new file mode 100644
index 000000000000000..eb90612e96b98b3
--- /dev/null
+++ b/html/browsers/browsing-the-web/navigating-across-documents/016-onclick-return-false-no-navigation.html
@@ -0,0 +1,44 @@
+<!doctype html>
+<link rel="help" href="https://html.spec.whatwg.org/multipage/browsing-the-web.html#navigating-across-documents">
+<title>Link with onclick navigates iframe and returns false, which will prevent the href navigation</title>
+<script src="/resources/testharness.js"></script>
+<script src="/resources/testharnessreport.js"></script>
+<div id="log"></div>
+<iframe id="test" name="test"></iframe>
+<a target="test" onclick="document.querySelector('iframe').src='call-parent-postmessage.html';reports.push('onclick');return false;" href="href.html">Test</a>
+
+<script>
+var test = async_test();
+var reports = [];
+
+window.onmessage = test.step_func(function(e) {
+  reports.push(e.data);
+
+  // "call-parent-postmessage" is expected last, if this is not received last or
+  // not received at all, the test must fail.
+  if (e.data === "call-parent-postmessage") {
+    assert_equals(reports[0], "click");
+    assert_equals(reports[1], "onclick");
+    assert_equals(reports[2], "call-parent-postmessage");
+    assert_equals(reports.length, 3);
+  } else {
+    throw new Error('onclick returns false, href navigation must not occur');
+  }
+  test.done();
+});
+
+test.step(function() {
+  reports.push("click");
+  document.querySelector("a").click();
+});
+</script>
+
+<!--
+1. This test creates an iframe and an anchor with both an `onclick` and `href`.
+2. The test "clicks" the anchor, triggering the `onclick` handler operation,
+    which will attempt to navigate the iframe. This navigation will be successful.
+3. Navigating the iframe to the anchor's `href` does not occur, because `onclick` returns false.
+4. If the semantics are implemented correctly, reports will be
+    ["click", "onclick", "call-parent-postmessage"]
+
+-->
diff --git a/html/browsers/browsing-the-web/navigating-across-documents/016-onclick-return-true-then-navigation.html b/html/browsers/browsing-the-web/navigating-across-documents/016-onclick-return-true-then-navigation.html
new file mode 100644
index 000000000000000..8e1cac7112b1e23
--- /dev/null
+++ b/html/browsers/browsing-the-web/navigating-across-documents/016-onclick-return-true-then-navigation.html
@@ -0,0 +1,45 @@
+<!doctype html>
+<link rel="help" href="https://html.spec.whatwg.org/multipage/browsing-the-web.html#navigating-across-documents">
+<title>Link with onclick navigates iframe and returns true, which allows the href navigation</title>
+<script src="/resources/testharness.js"></script>
+<script src="/resources/testharnessreport.js"></script>
+<div id="log"></div>
+<iframe id="test" name="test"></iframe>
+<a target="test" onclick="document.querySelector('iframe').src='call-parent-postmessage.html';reports.push('onclick');return true;" href="href.html">Test</a>
+
+<script>
+var test = async_test();
+var reports = [];
+
+window.onmessage = test.step_func(function(e) {
+  reports.push(e.data);
+
+  // "href" is expected last, if this is not received last or
+  // not received at all, the test must fail.
+  if (e.data === "href") {
+    assert_equals(reports[0], "click");
+    assert_equals(reports[1], "onclick");
+    assert_equals(reports[2], "href");
+    assert_equals(reports.length, 3);
+  } else {
+    throw new Error('navigating to href must abort not-yet-mature navigation');
+  }
+  test.done();
+});
+
+test.step(function() {
+  reports.push("click");
+  document.querySelector("a").click();
+});
+</script>
+
+<!--
+1. This test creates an iframe and an anchor with both an `onclick` and `href`.
+2. The test "clicks" the anchor, triggering the `onclick` handler operation,
+    which will attempt to navigate the iframe.
+3. Navigating the iframe to the anchor's `href` must abort the not-yet-mature
+    navigation that was started by the `onclick` handler.
+4. If the semantics are implemented correctly, reports will be
+    ["click", "onclick", "href"]
+
+-->
diff --git a/html/browsers/browsing-the-web/navigating-across-documents/call-parent-postmessage.html b/html/browsers/browsing-the-web/navigating-across-documents/call-parent-postmessage.html
new file mode 100644
index 000000000000000..3c677b0b90687ee
--- /dev/null
+++ b/html/browsers/browsing-the-web/navigating-across-documents/call-parent-postmessage.html
@@ -0,0 +1,6 @@
+<!doctype html>
+<script>
+window.onload = function() {
+  parent.postMessage("call-parent-postmessage", "*");
+};
+</script>
diff --git a/html/browsers/browsing-the-web/navigating-across-documents/click.html b/html/browsers/browsing-the-web/navigating-across-documents/click.html
index 8cb03b74d5ecee7..11a8f1a1c375de7 100644
--- a/html/browsers/browsing-the-web/navigating-across-documents/click.html
+++ b/html/browsers/browsing-the-web/navigating-across-documents/click.html
@@ -1,4 +1,6 @@
 <!doctype html>
 <script>
-parent.postMessage("click", "*");
+window.onload = function() {
+  parent.postMessage("click", "*");
+};
 </script>
