Code to standards and expect the browsers to implement those standards reasonably. Avoid the bleeding edge to support those held back at LTS versions of common

Code to standards and expect the browsers to implement those standards reasonably. Avoid the bleeding edge to support those held back at LTS versions of common browsers, or if you use new tricks make sure they don't make things unusable on older-but-LTS browsers. Whether you consider IE11 an LTS browser or not is a matter for you to decide (yes, as it will be getting security updates for some time still, or no as it is seven years old, not getting any feature/support updates, and support for it is deprecated by even its own manufacture's apps). Support accessibility by not using fancy things for the sake of it, and if you do something fancy make at least a little effort to have things degrade gracefully for those with accessibility issues. A lot of sites/apps skip this step, but shouldn't.