TH and SCOPE
Use of the TH and SCOPE tags combined with the CAPTION and SUMMARY tags will provide sufficient information for most newer screen readers to process simple tables. The TH tag is used to designate certain cells as row and column headers. Visually, the TH tag changes the text formatting to bold face and center in most browsers.
The SCOPE attribute in the TH tag is used to further define whether the header is a row ( <th scope=”col”> ) or a column ( <th scope=”row”> ). Designating the SCOPE changes the order in which a screen reader reads the cells. Otherwise, screen reader users would hear the table read in the default left-to-right, top to bottom. This code is sufficient for most screen readers to process simple tables (one header row and one header column), but additional tags are needed for more complex tables. See below for details.
When sighted users focus on a table cell, they are able visually determine which row and column the cell is in and what the data means. On the other hand, a screen reader can only read aloud each cell one by one from left to right top to bottom. One way to help blind users process the information is to read out what row and column header the cell refers too. In the table below, the headers are the top row (color names) and the left column (language names).