Accessible tables are structured with row and column headers. Screen readers use this information to speak information one cell at a time and provide context to users.

Only Use Tables for Data

Data doesn't have to mean percentages and decimals, it can be purely textual. A telephone or office directory can be data. Do not use tables to align text and images. This includes invisible tables. 

Keep Tables Simple

Use Headers

Make sure header cells are accurately explaining the data directly below (columns) or to the right (rows).