Header Tags
Source: WebAIM
When you use the table header (<th>) tag, most browsers cause the text to become bold and centered, which can be a nice visual effect, but the <th> tag should only be used in data tables. Don’t use it in layout tables because you may confuse screen reader users, making them think they’re inside a data table when they are not.
Adding a Header Tag in Dreamweaver

Captions and Summary in Dreamweaver
When you insert a Table, users have the option immediately to add a Caption and Summary to the table.

Tables in Pearson LearningStudio
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Users can create a table within the Visual Editor.
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You can create a “Section 508”-compliant table with the Table Wizard.
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Alternatively, you can convert an existing table to a “Section 508”-compliant table using the Table Properties context menu. Create a new table with the Table Wizard or open the Table Properties dialog.
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Click the “Accessibility” tab.
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In the “Accessibility” tab, fill in the fields: Heading rows/columns, Caption, and Summary about the table. Select the [Associate cells with headers] checkbox.
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The caption should specify the title of the table. For information about table captions http://www.w3.org/TR/WCAG20-TECHS/H39.html
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Summary is used to give more details on the contents of the table. This attribute only needs to be completed if user sets 2 for the Heading rows or Heading columns field. For more information about Summary attribute include link to http://www.w3.org/TR/WCAG20-TECHS/H73.html
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Always select the [Associate cells with headers] checkbox.
Resources
Data Tables
Table Captions and Summaries
Proportional Sizing