Mastering HTML DocTypes: Choosing the Right Structure for Your Website

DocTypes play a crucial role in HTML documents, as they set the foundation for how browsers interpret and render web pages. Selecting the correct DocType is essential to ensure compatibility across different browsers and maintain a consistent layout. In this blog post, we will explore various DocTypes and their implications for your website.

Choosing the Perfect DocType

Standards Mode, Cutting Edge Validation

<!DOCTYPE html>

This is the recommended DocType to use. It enables you to validate new HTML features such as <video>, <canvas>, and ARIA. Be sure to test your page on the latest browser versions for optimal results.

Standards Mode, Legacy Validation Target


This DocType also triggers the Standards mode but allows for less precise legacy validation. Use this option only if your organization insists on targeting legacy validation, although it is highly advisable to adopt <!DOCTYPE html> and advocate for revising your organization's policies.

Standards Mode Compatibility with Sliced Image Layouts

<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "">

If you rely on sliced images within table layouts and do not wish to modify them, this DocType provides an "Almost Standards" mode. Keep in mind that transitioning to HTML5 (and the full Standards mode) in the future may cause your layouts to break. It's recommended to make your designs Standards mode-compatible from the outset.

Embracing Quirks Mode: A Cautionary Tale

No DocType specified.

Designing for the Quirks mode intentionally is strongly discouraged. Such a decision may haunt you, your colleagues, or successors in the future. Instead, if you need to support older versions of Internet Explorer due to client requirements, it's better to utilize specific hacks using conditional comments than relying on the Quirks mode.

Handling IE Compatibility Issues

Scenario 1: Not on Microsoft's Blacklist, Avoiding Browser-Specific Cruft

No X-UA-Compatible HTTP header or meta tag required.

Scenario 2: On Microsoft's Blacklist or Concerned About Compatibility View

Include the following meta element (not valid in HTML5) before any script elements:

<meta http-equiv="X-UA-Compatible" content="IE=Edge">

Alternatively, set the following HTTP header on your page:

X-UA-Compatible: IE=Edge
Scenario 3: Site Breaks in Different IE Versions

For each scenario, include the respective meta element (not valid in HTML5) or set the corresponding HTTP header:

  • IE8 Compatibility: <meta http-equiv="X-UA-Compatible" content="IE=EmulateIE7"> or X-UA-Compatible: IE=EmulateIE7
  • IE9 Compatibility: <meta http-equiv="X-UA-Compatible" content="IE=EmulateIE8"> or X-UA-Compatible: IE=EmulateIE8
  • IE10 Compatibility: <meta http-equiv="X-UA-Compatible" content="IE=EmulateIE9"> or X-UA-Compatible: IE=EmulateIE9

Ensure you fix your site to eliminate reliance on non-standard behaviors and eventually migrate to IE=Edge.


Selecting the appropriate DocType is vital to ensure consistent rendering across browsers and avoid layout inconsistencies. By understanding the different DocTypes available and their implications, you can make informed decisions about structuring your HTML documents.

Remember to embrace the Standards mode whenever possible and handle compatibility issues with Internet Explorer strategically.

With the right DocType and compatibility measures in place, you can create web pages that perform optimally and provide a seamless user experience.