Webmaster in a Nutshell, Third Edition

The <th> and <td> Tags

The <th> (table header) and <td> (table data) tags go inside the <tr> tags of an HTML table to create the cells and contents of each cell within a row. The two tags operate similarly, except that header cells are typically rendered in bold text and centered by default. <td> cell contents are rendered in the regular base font, left-justified.

The align, valign, and other attributes work the same in the cell tags as they do in the row tag. When specified for <th> and <td>, these attributes override the same behavior set in the upper-level tags for their specific cell.

The other attributes to the cell tags are very important to the layout of your table. The width attribute can set the width of a table cell and all cells within its column. As with the <table> tag, a value may be given in an integer number of pixels or a percentage of the width of the table. A width value may be ignored by the browser if contents within the column have a fixed width larger than the value (i.e., an image or nonbreaking line of text). You should use only one width value in the cells of the same column. If two width values are specified in the same column of cells, the browser uses the larger value.

The nowrap attribute, when included in a cell tag, disables regular linebreaking of text within a table cell. With nowrap, the browser assembles the contents of a cell onto a single line, unless you insert a <br> or <p> tag, which forces a break.

Cell Spanning

It is common ...