Do browsers still render deprecated HTML?

Most still do, for backwards compatibility — but rendering is unreliable. Deprecated elements may render differently across browsers, may behave inconsistently with CSS, and may stop rendering at any future browser update. There's no commitment to keep deprecated elements working forever. The risk is silent breakage of pages you forgot to migrate.

Is the marquee tag really gone?

Officially deprecated since HTML 4, never part of HTML5. Most browsers still render it for legacy compatibility but with no guarantee. Replace with CSS animation if you need scrolling text, or — better — don't have scrolling text at all. It's an anti-pattern that hurts accessibility regardless of implementation.

What replaces frame and frameset?

For embedding external content: iframe (still supported, modern, has sandbox attributes for security). For multi-pane layouts: CSS Grid or Flexbox in a single document. The original purpose of frames (independent scrolling regions) is better served by CSS overflow: auto on a div in a single-document layout.

My CMS keeps generating deprecated tags from imported content — how to fix?

Old database content migrated from earlier CMS versions often contains , , etc. Use HTMLPurifier (PHP) or DOMPurify (JS) configured to strip deprecated tags during save. For existing content, a one-time database-level find-and-replace cleans up. Tools: Better Search Replace in WordPress, Liquid filters in Shopify, SQL UPDATE statements with REPLACE() for raw databases.

How to Fix Deprecated HTML Elements

Deprecated HTML elements — <center>, <font>, <marquee>, <frame>, <big>, <strike>, <tt> — still render in most browsers but have no guarantee. They appear most often in migrated content from old CMS installs and in templates that haven't been updated since 2010. This guide maps each deprecated element to its modern replacement and walks through bulk-fixing legacy content. For related fixes, see the HTML Checker Fixes index.

1. Get the full list

Step 1

Run the HTML Checker

Run the HTML Checker filtered to deprecated-element warnings. Export the CSV. Each row identifies the URL, line, and which deprecated element appears.

Step 2

Determine source: template or content

View source on a few flagged pages. Is the deprecated tag in template markup (header, footer, sidebar — fix once in the template) or in CMS-stored content (need bulk replacement in database)? Most are in content from old WYSIWYG editors.

2. The replacement table

Deprecated	Modern replacement
`<center>Content</center>`	`<div style="text-align:center">Content</div>` or a CSS class
`<font color="red" size="4">`	`<span style="color:red;font-size:1.2em">` or a CSS class
`<b>` (when stylistic only)	`<strong>` (semantic emphasis) or CSS `font-weight`
`<i>` (when stylistic only)	`<em>` (semantic emphasis) or CSS `font-style`
`<u>`	`<span style="text-decoration:underline">` (avoid — underline implies link)
`<strike>`	`<del>` (semantic deleted text) or `<s>` (no longer accurate)
`<big>`	CSS `font-size`
`<tt>`	`<code>`, `<samp>`, or `<kbd>` depending on intent
`<marquee>`	CSS animation or — better — remove (anti-pattern)
`<blink>`	Remove. Was never serious.
`<frame>`, `<frameset>`	`<iframe>` for embeds, CSS Grid/Flexbox for layout
`<applet>`	`<object>` (Java not supported anyway)
`<acronym>`	`<abbr>`
HTML attributes like `bgcolor`, `align`	CSS `background-color`, `text-align`

3. Fix templates first

Step 1

Search templates for deprecated patterns

SSH into the site or use SFTP:

grep -rE "<(center|font|marquee|big|strike|tt|frame|blink)" /var/www/yoursite/wp-content/themes/your-theme/

Each match is a template file that needs updating. Apply the replacement table above.

4. Bulk-replace in CMS content

WordPress: Better Search Replace

Step 1

Run targeted database replacements

WP Admin → Tools → Better Search Replace. Take a database backup first. Then for each deprecated pattern:

Search:  <center>
Replace: <div style="text-align:center">
Tables: wp_posts, wp_postmeta
Dry run: yes (first), then real run

Repeat for the closing tag and each deprecated element. The plugin handles serialised data correctly.

Shopify: Liquid filter approach

Step 1

Apply replace filters in templates

In theme.liquid or specific section templates, filter rich-text output:

{{ product.description 
   | replace: '<center>', '<div style="text-align:center">'
   | replace: '</center>', '</div>'
   | replace: '<font color="red">', '<span style="color:red">'
}}

Quick fix; the real cleanup is editing each product's description in the admin panel.

Raw SQL (any platform)

Step 1

Direct database replace

BACKUP FIRST. Then:

UPDATE wp_posts SET post_content = REPLACE(post_content, '<center>', '<div style="text-align:center">');
UPDATE wp_posts SET post_content = REPLACE(post_content, '</center>', '</div>');

⚠️ Raw SQL REPLACE can corrupt serialised PHP data (Yoast, Elementor metadata). Use Better Search Replace plugin for WordPress instead of raw SQL.

5. Prevent recurrence

Step 1

Configure WYSIWYG editor to strip deprecated tags

TinyMCE in WP: filter via tiny_mce_before_init with valid_elements excluding deprecated tags. Custom editors: configure allowed-element schema to omit deprecated tags.

Step 2

CI linting

Add a build-time check that fails the deploy if templates contain deprecated tags:

! grep -rE "<(center|font|marquee|big|strike|tt|frame|blink)" ./src/templates/

6. Re-validate

Re-run the HTML Checker. Deprecated-element warnings should clear or drop to a handful of legacy content pieces you'll fix manually.

📐 Re-run the HTML Checker

Verify deprecated elements are replaced with modern equivalents.

Run HTML Checker →