HTML and XHTML are the markup languages used to create a solid foundation for your website or web application, and articles in this category generally touch upon the semantics and accessibility aspects of marking up web pages.
Only use the fieldset and legend elements to group logically related form controls, always use both elements together, and keep legend texts short.
If you use an XHTML doctype with an XML declaration, Internet Explorer 6 will switch to Quirks mode and use an incorrect CSS box model.
Sam Ruby, co-chair of the W3C HTML Working Group, has put together a number of select quotes to illustrate the evolution of HTML, from the beginning to where it is now.
Using p elements instead of multiple br elements to create paragraphs in HTML makes your documents more accessible and easier to style.
The alt attribute is valid only for images and provides alternative text used when the image cannot be rendered. Do not use it with links and other non-image HTML elements.
There is nothing called a “CSS class” in HTML or CSS, so please refer to values of the HTML class attribute as classes or class names instead.
Combining the concept of diagnostic CSS with the Stylish Firefox extension makes it easy to apply CSS that reveals invalid or deprecated HTML to any site you want.
Validating WAI-ARIA in HTML or XHTML is currently more difficult than it could be, but it is possible and there is hope that it will be easier in the near future.
There is a simple rule that defines which characters you may use with the id attribute: begin with a letter, then add any number of digits, hyphens, underscores, colons, and periods.
What do you do when an HTML document’s main heading is not the first text that should be marked up as a heading - insert a dummy heading or give up on having a perfect document outline?
Always specify which natural language (spoken, written or signed human language) is used for a document’s content. Use the lang and/or xml:lang attributes for this.
The value of the id attribute must be unique in an HTML document. In other words, the same id value may only occur once.
It is quite common to come across images with missing alternative text or alternative text that does not properly describe the image’s content or function.
The Free Site Validator crawls an entire site, validates all pages it finds with the W3C validator, and verifies all links it finds on the site.
If screen readers reliably supported multiple labels for the same form control, it would be easier to make error messages and instructions fully accessible.
An analysis of the sites crawled by the bulk validation tool Nikita the Spider during March 2008.
By using the label element to associate form controls with their label text, you improve the accessibility of HTML forms and make styling and scripting them easier.
Teach people how to use plain old semantic HTML to create valid, well-structured, accessible and interoperable websites.
John Allsopp on the current and possible future states of semantics on the HTML based Web.