Why this is important: Simple data tables are those consisting of only one column header, and possibly one row header, for each data cell. Unless the HTML code explicitly associates each data cell with its column (and row, if applicable) header, visitors using text readers will hear only a string of unintelligible data values. Technically, this is done with the <th scope= ...> element. Text-only visitors also might need assistance in understanding the purpose of the table, which may be provided to them with the summary attribute of the <table> element. On the other hand, text-only visitors should never have to hear summaries such as "this table is for layout only."