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ADOBE ACROBAT 7.0
103
Section 13: Fixing advanced accessibility problems
Incorrect tagging structure for a table (top) and the corrected tagging structure for the table (bottom). The corrected structure has <TH> tags
for all header cells, including <TH> tags that are at the same level as the <TD> tags for rows that contain both types of cells.
Tables that are a straightforward grid provide the greatest accessibility. That is, each row has the same number of
columns, and each column has the same number of rows. Many tables, however, merge cells to make a single cell
span two or more columns or rows. Merging cells across columns or down rows creates problems for screen readers
unless you properly assign ColSpan and RowSpan attributes to the <TH> or <TD> tag of the merged cell. These
attributes tell the screen reader how many columns or rows a particular cell spans (such as ColSpan=3 for a cell that
is three columns wide, or RowSpan=2 for a cell that is two rows deep).
For tables that contain blank cells, you may also need to add empty <TD> cells into the tree structure, so that each
row or column has the same number of cells. This enables the screen reader to present the content in a way that
doesn't confuse the user.
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