“a11y” is a numeronym for the word “accessibility” where the first and last letters are retained and the rest are replaced by the number of letters in between.
The Web Content Accessibility Guidelines (WCAG) 2.0 is the international standard for web accessibility, and it provides a set of guidelines and recommendations for making web content more accessible. The guidelines are developed by the World Wide Web Consortium (W3C) and can be found on their website at the following link: https://www.w3.org/TR/WCAG20/
It’s important to note that accessibility is an ongoing process, and you should regularly test and update your website to ensure that it continues to conform to the latest accessibility guidelines. Additionally, you can also find more resources on accessibility testing and implementation at https://www.w3.org/WAI/resources/ and https://www.w3.org/WAI/standards-guidelines/wcag/
It is also worth mentioning that there are other organizations which are working on accessibility standards and guidelines, like the Accessible Rich Internet Applications (ARIA) specification, the Web Accessibility Initiative (WAI) and The Accessible Guidelines, all these standards and guidelines are aligned with WCAG 2.0 and they may provide additional information and guidance on specific accessibility topics.