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National Library of Medicine Web Application/Site Development Guidelines

This Style Guide for the National Library of Medicine (NLM) explains the markup and design requirements for all NLM Web projects, along with various standards and best practices. NLM Web pages must be authored in valid XHTML 1.0 Transitional and styled with valid Cascading Style Sheets and be coded in order to ensure accessibility.


NLM is committed to serving the entire public, and that means striving to ensure that all pages of our site are accessible to the greatest possible number of people and Assistive Technology devices.

Browsers and Scripts

NLM uses JavaScript in a selective manner. Pages should degrade gracefully when JavaScript is disabled. Any use of JavaScript should be cleared with your NLM project coordinator to assure it works well with existing site-wide implementations.

The use of XHTML markup aimed at a specific browser (e.g., Microsoft Internet Explorer) should be avoided. As of April 2014, NLM supports the following browsers: Internet Explorer 9/10, Safari 5, Mozilla Firefox 26 (minimum).


NLM recommends the use of the UTF-8 character set for Web pages so that non-English languages and diacritics are more effectively displayed. The coding to be placed in the HEAD tag of all Web pages is:

<meta http-equiv="Content-Type" content="text/html; charset=utf-8" />

Design Policies

NLM's Web design policies.

Header and Footer

Guidelines for appropriately branding a Web site or application in development for NLM, and when to use the official NLM header and footer.

NLM Main Web Site - Coding Instructions

Includes NLM's official Cascading Style Sheets. If you wish to create your own style sheets, please discuss your requirements with your NLM project coordinator.

NLM Main Web Site - Coding Examples

Web page examples showing how markup will display the NLM css.


Referring to an NLM product in print.

Web Applications

Quality assurance checklist for Web applications.

XHTML and CSS: Guidelines

NLM Web pages must be authored in XHTML 1.0 Transitional. All XHTML must validate.

Web pages 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.