Clean up mentions of HTML4 and XHTML (#3980)

A lot of HTML4 and XHTML descriptions were removed by #2490, but there
are still some parts left. This PR attempts to clean up those pieces.

## Modify link from HTML4 to HTML

F40 and F44

## Remove mentions of XHTML in techniques

ARIA6, SCR22, C27, F46, F58, F69, F70, F77, F80, G108, G110, G175 and
G204

## Remove mentions of XHTML in understanding

- keyboard
- pronunciation (potentially related
#2652)

---

However, the following pages are excluded:

[Understanding SC
3.1.1](https://www.w3.org/WAI/WCAG22/Understanding/language-of-page):

```html
<a href="https://www.w3.org/International/techniques/authoring-html#gslang">Internationalization Best Practices: Specifying Language in XHTML &amp; HTML Content</a>
```

This link text is probably inappropriate, but I didn't know what to
change it to, so I left it as it is.

[Understanding
Conformance](https://www.w3.org/WAI/WCAG22/Understanding/conformance):

In the Examples of Conformance Claims section, there are several
mentions of XHTML 1.0. I didn't change them in this PR, but I think it
needs to be rewritten separately.

---------

Co-authored-by: Patrick H. Lauke <[email protected]>

techniques/css/C27.html

@@ -21,7 +21,7 @@ <h2>Description</h2>
 		<p>There may also be situations where the visually presented order is necessary to the overall understanding of the page, and if the source order is presented differently, it may be much more difficult to understand. </p>
 		<p>When the source order matches the visual order, everyone will read the content and interact with it in the same (correct) order. </p>
 		<div class="note">
-			<p>The <code class="language-html">tabindex</code> attribute in HTML has two functions. One is to make an element focusable and the other is to assign the element a position in the focus order. A <code class="language-html">tabindex</code> of 0 makes an element focusable, but adds it to the focus order in the order of source elements. The focus order will follow positive values of tabindex in ascending order. Setting <code class="language-html">tabindex</code> values that result in an order different from the order of elements in the Document Object Model (DOM) can mean the order is incorrect for users of assistive technologies. This is largely because the tabindex property is specified in the HTML or XHTML and not the CSS. This may change in future specifications. It may also differ from the visual presentation order. </p>
+			<p>The <code class="language-html">tabindex</code> attribute in HTML has two functions. One is to make an element focusable and the other is to assign the element a position in the focus order. A <code class="language-html">tabindex</code> of 0 makes an element focusable, but adds it to the focus order in the order of source elements. The focus order will follow positive values of tabindex in ascending order. Setting <code class="language-html">tabindex</code> values that result in an order different from the order of elements in the Document Object Model (DOM) can mean the order is incorrect for users of assistive technologies. This is largely because the tabindex property is specified in the HTML and not the CSS. This may change in future specifications. It may also differ from the visual presentation order. </p>
 		</div>
 	</section>
 	<section id="examples">

techniques/failures/F40.html

@@ -56,8 +56,8 @@
 
          <ul>
             <li> 
-                  <a href="https://www.w3.org/TR/html401/struct/global.html#h-7.4.4">HTML 4.01 META element</a> 
-               </li>
+              <a href="https://html.spec.whatwg.org/multipage/semantics.html#the-meta-element">HTML - the <code class="language-html">meta</code> element</a>
+            </li>
          </ul>
    </section>
 </body>

techniques/failures/F44.html

@@ -62,8 +62,9 @@
    </ul></section><section id="resources"><h2>Resources</h2>
 
          <ul>
-            <li>HTML 4.01 <a href="https://www.w3.org/TR/html4/interact/forms.html#adef-tabindex">Tabbing navigation</a> 
-               </li>
+            <li>
+              <a href="https://html.spec.whatwg.org/multipage/interaction.html#the-tabindex-attribute">HTML - the <code class="language-html">tabindex</code> attribute</a>
+            </li>
          </ul>
    </section>
 </body></html>

techniques/failures/F46.html

@@ -18,7 +18,7 @@
                <code class="language-html">scope</code> attributes 
               </li>
       </ul>
-      <p>Assistive technologies use the structure of an HTML or XHTML table to present data to
+      <p>Assistive technologies use the structure of an HTML table to present data to
                         the user in a logical manner. The th element is used to mark
                         the column and row headers of the table. A screen reader uses the
                         information in th elements to speak the header information that

techniques/failures/F58.html

@@ -30,8 +30,7 @@
       response.setContentType("text/html");
 PrintWriter out = response.getWriter();
 response.setHeader("Refresh", "10; URL=TargetPage.html");
-out.println("<!DOCTYPE html PUBLIC \"-//W3C//DTD XHTML 1.0 Transitional//EN\"
-   \"https://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd\">");
+out.println("<!DOCTYPE html>");
 out.println("<html><head><title>Redirect</title></head><body>");
 out.println("<p>This page will redirect you in 10 seconds.</p>");
 out.println("</body></html>");

techniques/failures/F69.html

@@ -1,5 +1,5 @@
 <!DOCTYPE html><html lang="en" xml:lang="en" xmlns="http://www.w3.org/1999/xhtml"><head><title>Failure of Success Criterion 1.4.4 when resizing visually rendered text up to 200 percent causes the text, image or controls to be clipped, truncated or obscured</title><link rel="stylesheet" type="text/css" href="../../css/editors.css" class="remove"/></head><body><h1>Failure of Success Criterion 1.4.4 when resizing visually rendered text up to 200 percent causes the text, image or controls to be clipped, truncated or obscured</h1><section class="meta"><p class="id">ID: F69</p><p class="technology">Technology: failures</p><p class="type">Type: Failure</p></section><section id="applicability"><h2>When to Use</h2>
-      <p>HTML, XHTML and CSS</p>
+      <p>HTML and CSS</p>
    </section><section id="description"><h2>Description</h2>
       <p>The objective of this failure condition is to describe a problem that occurs when changing the size of text causes text to be clipped, truncated, or obscured, so that it is no longer available to the user. In general, this failure occurs when there is no way for a user agent's layout engine to honor all the layout hints in the HTML at the new font size. Some of the ways in which this can occur include:</p>
       <ul>

techniques/failures/F70.html

@@ -4,7 +4,7 @@
 obsoleteSince: 22
 ---
 <!DOCTYPE html><html lang="en" xml:lang="en" xmlns="http://www.w3.org/1999/xhtml"><head><title>Failure of Success Criterion 4.1.1 due to incorrect use of start and end tags or attribute markup</title><link rel="stylesheet" type="text/css" href="../../css/editors.css" class="remove"/></head><body><h1>Failure of Success Criterion 4.1.1 due to incorrect use of start and end tags or attribute markup</h1><section class="meta"><p class="id">ID: F70</p><p class="technology">Technology: failures</p><p class="type">Type: Failure</p></section><section id="applicability"><h2>When to Use</h2>
-      <p>Markup languages: HTML, XHTML, and other SGML or XML-based technologies.</p>
+      <p>Markup languages: HTML, and other SGML or XML-based technologies.</p>
    </section><section id="description"><h2>Description</h2>
       <p>The objective of this failure is to identify examples of markup errors in element tags that could cause assistive technology to be unable to generate a satisfactory model of the page. Different user agents may implement different heuristics to recover from errors, resulting in inconsistent presentations of the page between user agents.</p>
       <p>Some common types of problems with start and end tags that lead to this failure condition (though this is not an exhaustive list):</p>

techniques/failures/F77.html

@@ -4,7 +4,7 @@
 obsoleteSince: 22
 ---
 <!DOCTYPE html><html lang="en" xml:lang="en" xmlns="http://www.w3.org/1999/xhtml"><head><title>Failure of Success Criterion 4.1.1 due to duplicate values of type ID</title><link rel="stylesheet" type="text/css" href="../../css/editors.css" class="remove"/></head><body><h1>Failure of Success Criterion 4.1.1 due to duplicate values of type ID</h1><section class="meta"><p class="id">ID: F77</p><p class="technology">Technology: failures</p><p class="type">Type: Failure</p></section><section id="applicability"><h2>When to Use</h2>
-      <p>HTML, and any XML-based markup languages including XHTML and SVG</p>
+      <p>HTML, and any XML-based markup languages including SVG</p>
    </section><section id="description"><h2>Description</h2>
       <p>This describes a failure condition where duplicate <code class="language-html">id</code> errors are known to cause problems for assistive technologies when they are trying to interact with content. Duplicate values of type <code class="language-html">id</code> can be problematic for user agents that rely on this attribute to accurately convey relationships between different parts of content to users. For example, a screen reader may use <code class="language-html">id</code> values to identify the applicable header content for a data cell within a data table, or an input control to which a given label applies. If these values are not unique, the screen reader will be unable to programmatically determine which headers are associated with the data cell or which control is associated with which label or name.</p>
       <p>Checking that <code class="language-html">id</code> attribute values are unique within a document can be done by validating the document against its specification, because the specification defines which attributes contain document-wide unique identifiers.</p>

techniques/failures/F80.html

@@ -1,5 +1,5 @@
 <!DOCTYPE html><html lang="en" xml:lang="en" xmlns="http://www.w3.org/1999/xhtml"><head><title>Failure of Success Criterion 1.4.4 when text-based form controls do not resize when visually rendered text is resized up to 200%</title><link rel="stylesheet" type="text/css" href="../../css/editors.css" class="remove"/></head><body><h1>Failure of Success Criterion 1.4.4 when text-based form controls do not resize when visually rendered text is resized up to 200%</h1><section class="meta"><p class="id">ID: F80</p><p class="technology">Technology: failures</p><p class="type">Type: Failure</p></section><section id="applicability"><h2>When to Use</h2>
-      <p>HTML, XHTML, and CSS</p>
+      <p>HTML and CSS</p>
    </section><section id="description"><h2>Description</h2>
       <p>The objective of this failure condition is to describe a problem that occurs when changing the size of text does not cause the text-based form controls to resize accordingly. This means that the user may have difficulty entering text and being able to read what they have entered because the text is not displayed at the text size required by the user.</p>
       <p>Text-based form controls include input boxes (text and textarea) as well as buttons.</p>

techniques/general/G108.html

@@ -20,7 +20,7 @@
    </section><section id="examples"><h2>Examples</h2>
       <section class="example">
 
-            <p>Example 1: A Web page written in HTML or XHTML uses standard form
+            <p>Example 1: A Web page written in HTML uses standard form
                 controls, and identifies the form control using the title attribute.
                 The user agent makes information about these controls, including the
                 name, available to assistive technology through the DOM and through

techniques/general/G110.html

@@ -19,7 +19,7 @@ <h3>HTML:
 
               Refresh With a URI and No Timeout</h3>
 
-            <p>In HTML 4.x and XHTML 1.x, it is possible to implement a client-side
+            <p>In HTML, it is possible to implement a client-side
                 redirect using the
 
                   meta

techniques/general/G175.html

@@ -17,7 +17,7 @@
             	<img src="img/opencolorpicker.jpg"/>
             	<figcaption>Screenshot showing the color selection tool with the color picker opened to select a color for the foreground. The user is presented with a choice of 216 colors.</figcaption>
             </figure>
-            <p class="working-example">Here is a working example of this technique implemented using PHP, Javascript, CSS and XHTML:
+            <p class="working-example">Here is a working example of this technique implemented using PHP, Javascript, CSS and HTML:
                 <a href="../../working-examples/colour-picker/">Color Picker Example</a>.</p>
 
       </section>

techniques/general/G204.html

@@ -2,7 +2,7 @@
       <p>All technologies</p>
    </section><section id="description"><h2>Description</h2>
       <p>This technique helps avoid situations where horizontal scrolling may occur. Many people with cognitive disabilities and low vision users who do not use assistive technology have a great deal of trouble with blocks of text that require horizontal scrolling. It involves not interfering with the reflow of text if the window is narrowed. One of the best ways to do this is to define widths of text block containers in percentages.</p>
-      <p>HTML and XHTML user agents automatically reflow text as the browser window is narrowed as long as the author does not specify widths using absolute measurements such as pixels or points. </p>
+      <p>HTML user agents automatically reflow text as the browser window is narrowed as long as the author does not specify widths using absolute measurements such as pixels or points. </p>
    </section><section id="examples"><h2>Examples</h2>
       <section class="example">
 

understanding/20/keyboard.html

@@ -245,7 +245,7 @@ <h3>Additional Techniques (Advisory) for Keyboard</h3>
 
          <ul>
 
-            <li>Using XHTML role, state, and value attributes if repurposing static elements as interactive
+            <li>Using WAi-ARIA role, state, and value attributes if repurposing static elements as interactive
                user interface components (future link) AND 
                <a href="../Techniques/client-side-script/SCR29" class="script">Adding keyboard-accessible actions to static HTML elements</a>
 

understanding/20/pronunciation.html

@@ -82,7 +82,7 @@ <h2>Examples of Pronunciation</h2>
                twice: the Han characters (Kanji) that can be pronounced in a wrong way are read first
                and then kana is spoken in order to provide the correct reading.</dd>
          <dt>Showing the reading of the words by ruby element</dt>
-         <dd>Web content using XHTML 1.1 provides kana (phonetic syllabary characters) written
+         <dd>Web content using HTML provides kana (phonetic syllabary characters) written
                above the characters to show the reading (pronunciation) of the words by using the
                ruby element.</dd>
          <dt>Providing sound files of the pronunciation</dt>
@@ -154,7 +154,7 @@ <h3>Sufficient Techniques for Pronunciation</h3>
 
             <li> 
 
-               <a href="../Techniques/html/H62" class="html">Using the ruby element</a> (XHTML 1.1)
+               <a href="../Techniques/html/H62" class="html">Using the ruby element</a>
 
             </li>