Standards Summary

Meaning and Presentation

Today with the power of CSS there is no need in using HTML to style. Thus, meaning (HTML) can be separated from presentation (CSS).The advantages are obvious – it can greatly decrease file sizes, it has flexibility of a central style sheet and it also can produce pages of greater accessibility.

In other words, you should not style anything within the HTML and use such tags as font or such attributes as bgcolor. Even the border attribute inside an img tag is not valid in XHTML 1.1. However, there is no styling that can be done even better with CSS than in HTML.

It doesn’t mean you should avoid the presentation from HTML. The application of meaning means that specific HTML tags should be used when appropriate. For example, h1, h2 etc. should be used for headings and you should not just use CSS to make fonts larger.
You should not use tables for layout. It completely changes the way the HTML has traditionally been structured in the past but it reduces the size of the page and becomes more accessible.

Tags

All tags In XHTML should be lowercase and must be closed. The tags that do not have closing tags (such as br and img) must close themselves with a ‘/’ at the end (such as <br />).

Note that there should be a space before the forward-slash.

The markup must be well formed, with elements properly nested (for example, <strong><em>this</em></strong>, not <strong><em>this</strong></em>).

All documents must have html, head, title and body elements. They must also start with a document type declaration.

The body of the document should start with p, h1, h2, h3, h4, h5, h6, div, pre, address, ins or del.

Attributes

All attributes must be lowercase with their values in quotation marks.

Minimized attributes are not allowed (such as <input type=”checkbox” checked />). As a rule, minimized attributes should be given the value that is the same as the name of the attribute (such as <input type=”checkbox” checked=”checked” />).
The name attribute is no longer valid and should be replaced with id (except in form elements).

The target attribute is not a valid attribute.

The alt attribute in the img tag is compulsory.

Accessibility

With the increasing legal implications to enforce certain accessibility the reasons to make web pages accessible to users with disabilities are not only moralistic but also advantageous. In case you follow the above mentioned practices, your HTML should already be accessible to users with minor (usually visual) impairments.

Reference: www.htmldog.com/guides/htmladvanced/recap/