To avoid accessibility problems for people who aren't able to see the image, you should provide a text description using the alt and longdesc attributes. In addition, avoid the use of server-side image maps. Note that in this DTD there is no name attribute.

When authoring document is HTML or XHTML, it is important to Add a Doctype declaration. This makes sure the document will be parsed the same way by different browsers.

There are no substantive changes in this document - only the integration of various errata. This document has been produced as part of the W3C HTML Activity. At the time of publication, the working group believed there were zero patent disclosures relevant to this specification.

Note: The HTML validator at http://w3.org does not complain when the xmlns attribute is missing in an XHTML document. This is because the namespace "xmlns=http://www.w3.org/1999/xhtml" is default, and will be added to the <html> tag even if you do not include it.

All HTML documents must start with a <!DOCTYPE> declaration. The declaration is not an HTML tag. It is an "information" to the browser about what document type to expect. In HTML 5, the declaration is simple: Tip: The <!DOCTYPE> declaration is NOT case sensitive.

For example, if you are using XHTML 1.0 directly, use the FPI in the DOCTYPE declaration, with the xmlns attribute on the document element to identify the default namespace:

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Doctype, or document type declaration, tells the browser which version of HTML the page is written in and which Document Type Definition (DTD) it should use. It is required for proper rendering and standards compliance; older versions of Internet Explorer may behave unpredictably without it.

An XHTML DTD describes the allowed syntax and grammar of XHTML markup. Every XHTML document must start with a DTD declaration and a line of code that declares that you are starting to write XHTML code. This is the mandatory minimum way to start an XHTML document:

Such a declaration is required when the character encoding of the document is other than the default UTF-8 or UTF-16 and no encoding was determined by a higher-level protocol. Here is an example of an XHTML document. In this example, the XML declaration is included.