Of a sample of approximately 8900 home pages from a list of of the top 10,000 sites the following HTML doctype usage was found:
Total pages with a doctype declaration: 7708
- XHTML 1.0: 4930 – 55%
- HTML5: 1539 -17%
- HTML 4.01: 960 – 11%
- XHTML 1.1: 111 – 1.3%
- HTML 4.0: 96 – 1%
- XHTML+RDFa: 24 -0.3%
- HTML 3.2: 9 – 0.1%
- html SYSTEM: 9 – 0.1%
- XHTML Mobile: 4
- html 2.0: 1
- other: 34 – 0.4%
doctype data text file (zip 5k)
DOCTYPE’s and Accessibility
To my knowledge the use of any particular DOCTYPE has absolutely no effect upon the accessibility of the associated HTML code. What is important is that the doctype you use does not trigger browser quirks mode. The simplest doctype to use to ensure that quirks mode is not triggered is the HTML5 doctype:
<!DOCTYPE html>
For data set and other details refer to: HTML5 Accessibility Chops: data for the masses