"Purplemath's algebra lessons are written with the student in mind. These lessons emphasize the practicalities rather than the technicalities, demonstrating dependable techniques, warning of likely "trick" questions, and pointing out common mistakes. The lessons are cross-referenced to help you find related material, and a "search" box is on every page to help you find what you're looking for.
While several federal laws address web accessibility, the most widely adopted and comprehensive technical standards have emerged not from a law, but from the W3C Web Content Accessibility Group. The WCAG standard is the most detailed, up-to-date guideline for creating accessible web content.