What to do first.
FIX FIRST
Colour contrast, which affects the most people Form labels, which block task completion Keyboard access, which blocks use entirely Alt text on meaningful images Missing page language
Those five cover most of the practical impact.
FIX SECOND
Heading structure Link text Error messages Focus indicators Skip links
FIX LATER
Complex component behaviour Advanced markup Edge cases
WHAT TO DO IMMEDIATELY REGARDLESS
Anything that blocks a task entirely: a form that cannot be submitted by keyboard, a menu that cannot be opened.
Those are not degradations; they are exclusions.
WHERE TO START
Your most visited pages, and any page where a task is completed: contact, checkout, booking.
An inaccessible contact form is a customer who cannot reach you.
THE REALISTIC APPROACH
An hour a week for a few weeks fixes most of what matters on a small site.
Not a project. A series of small corrections.