People with partial vision and low vision enlarge text to make it more readable. Using user-scalable=”no” in the <meta name=”viewport” element blocks people from resizing text, and ultimately from using your site.
Keyboard users use the “Tab” key to navigate from link to link on a web page. Without a “Skip to main” link (sometimes referred to as a “skip navigation link”), users are forced to tab through every link in a navigation bar before getting to the main content.
The title element, contained in the document's head element, is often the first piece of information announced by assistive technology. This helps tell people what page or view they are going to start navigating.
Setting the language on a webpage allows more people to access your content. This benefits people who use assistive technologies like text-to-speech, people who rely on captions, and people who have a hard time reading written material.