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XHTML: Guidelines

National Library of Medicine (NLM) Web pages must be authored in structural XHTML 1.0 Transitional. Page authors should follow accessibility guidelines in compliance with Section 508 and the WAI so that our site’s content will be made available to the widest possible number of people, browsers, and Internet devices. In addition, all XHTML must validate.

What is XHTML?
A introduction to XHTML.
XHTML Accessibility
Making sure your pages can be read by all visitors, browsers, and devices.
XHTML Validation
Ensure interoperability by avoiding errors and sticking to coding standards.

CSS: Style Sheets & Tips

Web sites and web-based applications must use valid Cascading Style Sheets (CSS) to control typography, color, and other layout elements. Style sheets must be linked in a way that accommodates the capabilities of new and old browsers.

Cascading Style Sheets
What is CSS?
NLM Style Sheets
NLM's official Cascading Style Sheets.
CSS Validation
Ensure style sheets are error-free.

If you wish to create your own style sheets, please discuss your requirements with your NLM project coordinator.