Html – Why won’t elements validate in HTML 4.01</h1> </header> <p style='font-size:1.2em'><span class="mr-2 badge badge-success">html</span><span class="mr-2 badge badge-info">html4</span><span class="mr-2 badge badge-warning">iframe</span><span class="mr-2 badge badge-primary">w3c-validation</span></p> <ins class="adsbygoogle" style="display:block" data-ad-client="ca-pub-8728145350222960" data-ad-slot="5017103864" data-ad-format="auto" data-full-width-responsive="true"></ins> <script> (adsbygoogle = window.adsbygoogle || []).push({}); </script> <div class="entry-content"> <p>I was just checking to see if it was valid to put an <code><iframe></code> element inside a <code><noscript></code> element as a fall back for displaying dynamic content. It validated fine with the HTML 5 doctype, but for HTML 4.01, I get the following error:</p> <blockquote> <p><strong>Line 9, Column 35: element "IFRAME" undefined</strong><br /> <iframe name="test" src="test.htm"></iframe></p> <p>You have used the element named above in your document, but the document type you are using does not define an element of that name. This error is often caused by:</p> <ul> <li>incorrect use of the "Strict" document type with a document that uses frames (e.g. you must use the "Frameset" document type to get the "" element),</li> <li>by using vendor proprietary extensions such as "" or "" (this is usually fixed by using CSS to achieve the desired effect instead).</li> <li>by using upper-case tags in XHTML (in XHTML attributes and elements must be all lower-case).</li> </ul> </blockquote> <p>This is what I whittled the HTML down to:</p> <pre><code><!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01//EN" "http://www.w3.org/TR/html4/strict.dtd"> <html> <head> <title>I AM YOUR DOCUMENT TITLE REPLACE ME</title> <meta http-equiv="Content-Type" content="text/html; charset=UTF-8"> </head> <body> <div> <iframe name="test" src="test.htm"></iframe> </div> </body> </html> </code></pre> <p>The <code><iframe></code> element is defined in the HTML 4.01 specification at the following URL: <a href="http://www.w3.org/TR/html401/present/frames.html#h-16.5" rel="nofollow noreferrer">http://www.w3.org/TR/html401/present/frames.html#h-16.5</a>.</p> <p>It passes with a transitional doctype, so I guess my question is "Why is it disallowed in a strict doctype, even though it's defined in the specification?".</p> </div> <div id="comments" class="comments-area"> <div class="row"> <div class="col-12"> <div class="mt-3 border-bottom border-success"> <h4 class="text-success"><i class='fa fa-check-circle text-success mr-3'></i><span>Best Answer</span></h4> </div> <div class='bg-transparent mb-3'> <blockquote> <p>"Why is it disallowed in a strict doctype, even though it's defined in the specification?</p> </blockquote> <p>Lots of things are defined in the specification but not allowed in Strict. <code><font></code> springs to mind. These are the things that the developers of the specification considered in need of documenting, were in use in browsers in the day, but which should be transitioned away from.</p> <p>I can think of two reasons why they might have thought that:</p> <ul> <li>"<a href="https://stackoverflow.com/questions/362730/are-iframes-considered-bad-practice" rel="nofollow ugc">Why do iframes suck?</a>". </li> <li><code><iframe></code> does (in theory) little that can't be achieved with <code><object></code></li> </ul> </div> </div> <div class="col-4"></div> </div> </div> <div id="related-embeded" class="related-embeded-area"><div class="row"><div class="col-12"><div class="mt-3 border-bottom border-success"><h4 class="text-info"><i class='fa fa-check-circle text-info mr-3'></i><span>Related Solutions</span></h4></div><div class="mt-3 mb-3 border-bottom"><h5><a href='https://itecnotes.com/tecnote/javascript-why-dont-self-closing-script-elements-work/'>Javascript – Why don’t self-closing script elements work</a></h5></div><div class='bg-transparent mb-3'> <p>XHTML 1 specification says:</p> <p><a href="http://www.w3.org/TR/xhtml1/#C_3" rel="noreferrer nofollow ugc">С.3. Element Minimization and Empty Element Content</a></p> <blockquote> <p>Given an empty instance of an element whose content model is not <code>EMPTY</code> (for example, an empty title or paragraph) do not use the minimized form (e.g. use <code><p> </p></code> and not <code><p /></code>).</p> </blockquote> <p><a href="http://www.w3.org/TR/xhtml1/dtds.html#a_dtd_XHTML-1.0-Strict" rel="noreferrer nofollow ugc">XHTML DTD</a> specifies script elements as:</p> <pre><code> <!ELEMENT script (#PCDATA)> </code></pre> </div><div class="mt-3 mb-3 border-bottom"><h5><a href='https://itecnotes.com/tecnote/javascript-embedding-content-iframes-with-an-html-4-01-doctype/'>Javascript – Embedding Content (iframes) with an HTML 4.01 doctype</a></h5></div><div class='bg-transparent mb-3'> <p>The iframe is not included as part of HTML 4.01 strict. see <a href="http://www.w3schools.com/tags/ref_html_dtd.asp" rel="nofollow ugc">http://www.w3schools.com/tags/ref_html_dtd.asp</a> to see what tags are supported by what doc types.</p> </div></div></div></div> </div> <div class="col-12 col-md-4"> <ins class="adsbygoogle" style="display:block" data-ad-client="ca-pub-8728145350222960" data-ad-slot="2985450245" data-ad-format="auto" data-full-width-responsive="true"></ins> <script> (adsbygoogle = window.adsbygoogle || []).push({}); </script> <div class='mt-3 ml-4 border-bottom border-success'><h6><span>Related Topic</span></h6></div><ul class='list-group list-group-flush'><li class="list-group-item"><a href='https://itecnotes.com/tecnote/html-how-to-use-if-else-condition-to-change-doctype-according-to-the-browser-in-html-file/'>Html – How to use if else condition to change doctype according to the browser in html file.</a></li><li class="list-group-item"><a href='https://itecnotes.com/tecnote/html-what-are-pros-to-use-xhtml-1-0-strict-with-contenttext-html-over-html-4-01-strict/'>Html – What are pros to use XHTML 1.0 strict with content=”text/html; over HTML 4.01 strict</a></li><li class="list-group-item"><a href='https://itecnotes.com/tecnote/html-force-internet-explorer-8-browser-mode-in-intranet/'>Html – Force “Internet Explorer 8” browser mode in intranet</a></li><li class="list-group-item"><a href='https://itecnotes.com/tecnote/html-where-is-the-html5-document-type-definition/'>Html – Where is the HTML5 Document Type Definition</a></li><li class="list-group-item"><a href='https://itecnotes.com/tecnote/html-why-does-html-think-chucknorris-is-a-color/'>Html – Why does HTML think “chucknorris” is a color</a></li><li class="list-group-item"><a href='https://itecnotes.com/tecnote/jquery-from-cdn/'>Jquery from cdn</a></li></ul> <ins class="adsbygoogle" style="display:block" data-ad-client="ca-pub-8728145350222960" data-ad-slot="8970621700" data-ad-format="auto" data-full-width-responsive="true"></ins> <script> (adsbygoogle = window.adsbygoogle || []).push({}); </script> </div> </div> <footer class="entry-footer"> </footer> </article> </div> </div> </div> </main> </div> </div> <footer id="colophon" class="site-footer"> <div class="site-info"> </div> </footer> </div> <script type='text/javascript' src='https://cdnjs.cloudflare.com/ajax/libs/jquery/1.12.4/jquery.min.js?ver=1.12.4' id='jquery-js'></script> <script type='text/javascript' id='jquery-js-after'> jQuery(document).ready(function ($) { const elements = document.getElementsByClassName("js-post-notice"); while(elements.length > 0){ elements[0].parentNode.removeChild(elements[0]); } }) </script> <script type='text/javascript' src='https://cdnjs.cloudflare.com/ajax/libs/twitter-bootstrap/4.3.1/js/bootstrap.min.js?ver=4.3.1' id='bootstrap4-js'></script> <script type='text/javascript' src='https://itecnotes.com/wp-includes/js/comment-reply.min.js?ver=5.9.10' id='comment-reply-js'></script> </body> </html>