The summary.
FOUR THINGS EVERY DOCUMENT NEEDS
The document type, the language declared, the character encoding, and the viewport setting.
Without the viewport setting, a page renders as a shrunken desktop layout on a phone.
CHOOSE ELEMENTS BY MEANING, NOT APPEARANCE
Visual weight conveys nothing to a screen reader. Choose the correct heading level and style it.
Read only the headings, in order — that reveals missing structure immediately.
LINK TEXT MUST MAKE SENSE OUT OF CONTEXT
Screen reader users list links and read them without surrounding text, which rules out "click here" and "read more".
A link navigates; an action that changes something is a button.
ALWAYS SPECIFY IMAGE DIMENSIONS
So the browser reserves space and the layout does not shift as images load, making people click the wrong thing.
NEVER USE PLACEHOLDER TEXT AS A LABEL
It disappears on typing and is handled inconsistently by assistive technology.
NEVER USE TABLES FOR LAYOUT
And mark header cells properly, so a screen reader announces which column a value belongs to.
