Current Scopes of Work contain a list of supported browsers and versions. Here's my proposal for a more modern alternative.
It's meant as a partner to the front-end development process section of the Engineering Ways of Working.
Praekelt builds sites using Progressive Enhancement: that means that support is treated as a continuum rather than a list of what is and what isn't supported. Every device with a browser is supported, but the target audience will guide where most development time will be spent on optimisation. Different browsers will be served different experiences; they will be thematically consistent and may be quite similar, but will not be identical.
A basic, functional, experience is delivered to every browser. JavaScript is not required for any key functionality; it is used to test the capabilities of the browser and enhance the experience by loading in additional CSS and JavaScript matching the capabilties of the browser. Rather than grading browsers, each component (in HTML, CSS, and JS) of a site is graded and the browser served the version that best meets its capabilties.
At one end of the scale are browsers on feature phones: they are served basic HTML, CSS, and small images. At the other end of the scale is the latest version of a browser on a desktop computer: they are served an experience enhanced with the latest CSS and Javascript techniques.
Internet Explorer is notoriously difficult. The amount of time spent optimising for various versions of IE should be determined by your user base.