The first step to achieve an accessible website is to use the right HTML element at all times. Try to write a code that reflects the structure of your information, do not stay in a simple set of
<span> which you will later style with CSS.
For example, if you want to make a button, don't simulate its behavior with a
<div> that you fill in with CSS and JS to achieve what the browser already gives you natively. The browser can already do a lot of your work if you use
To find out how accessible each element of HTML5 is, you can use HTML5 Accessibility, which is up-to-date and offers very reliable information.
If the HTML that you deliver to the browser has a meaning, that will help any type of device to understand it and offer the user the best experience, and that includes a computer, a mobile phone, a tablet, a screen reader, a voice recognition software, a watch ...
Remember, accessibility starts with semantics.