Table Cells (TH and TD)

The TH and TD elements are used for table cells. TH is used for table header cells while TD is used for table data cells. This distinction gives user agents a means to render such cells distinctly, for instance by using a larger or heavier font for header cells. It is also needed when rendering to speech. The CLASS attribute can be used to further differentiate cells, for instance into heads and subheads. This can be used together with style sheets to control the cell border style, and fill color etc.

The horizontal and vertical alignment of cell contents are determined by the ALIGN and VALIGN attributes respectively. In their absence, the alignment will be inherited from the TR element for the row. The COLSPEC attribute of the enclosing TABLE element provides a convenient way of specifying the default horizontal alignment for columns.

The AXIS and AXES attributes can be used when rendering to speech to provide abbreviated names for each cell's headers. Another application is when you want to be able to later process table contents to enter them into a database. Theses attributes are then used to give database field names. The table's class attribute should be used to let the software recognise which tables can be treated in this way.

Note: Disabling word wrap and using the <BR> element in order to control cell widths is discouraged in favor of using the table COLSPEC and WIDTH attributes.

Permitted Attributes for the TH/TD Element

ID

An SGML identifier used as the target for hypertext links or for naming particular elements in associated style sheets. Identifiers are NAME tokens and must be unique within the scope of the current document.

LANG

This is one of the ISO standard language abbreviations, e.g. "en.uk" for the variation of English spoken in the United Kingdom. It can be used by parsers to select language specific choices for quotation marks, ligatures and hypenation rules etc. The language attribute is composed from the two letter language code from ISO 639, optionally followed by a period and a two letter country code from ISO 3166.

CLASS

This a space separated list of SGML NAME tokens and is used to subclass tag names. By convention, the class names are interpreted hierarchically, with the most general class on the left and the most specific on the right, where classes are separated by a period. The CLASS attribute is most commonly used to attach a different style to some element, but it is recommended that where practical class names should be picked on the basis of the element's semantics, as this will permit other uses, such as restricting search through documents by matching on element class names. The conventions for choosing class names are outside the scope of this specification.

COLSPAN

The number of columns spanned by this cell. This allows you to merge cells across columns. It defaults to 1 (one).

ROWSPAN

The number of rows spanned by this cell. This allows you to merge cells across rows. It defaults to 1 (one).

ALIGN

The ALIGN attribute can be used to explicitly specify the horizontal alignment of paragraphs within a table row:

align=left

Paragraphs are rendered flush left. This is the default for data cells (TD).

align=center

Paragraphs are centered. This is the default for header cells (TH).

align=right

Paragraphs are rendered flush right.

align=justify

Text lines are justified where practical, otherwise this gives the same effect as the align=left setting.

align=decimal

Text lines are indented such that the first occurrence of a decimal point on each line are aligned vertically. If a line doesn't contain a decimal point, the line is rendered flush left for data cells and centered for header cells.

Note: In the absence of the ALIGN attribute, the default is overridden by the presence of an ALIGN attribute on the parent TR element, or by the COLSPEC attribute on the TABLE element. The COLSPEC attribute takes precedence over the TR element though!

DP

This specifies the character to be used for the decimal point with the ALIGN attribute, e.g. dp="." (the default) or dp=",". The default may be altered by the language context, as set by the LANG attribute on enclosing elements.

VALIGN

The VALIGN attribute can be used to explicitly specify the vertical alignment of material within a table cell:

valign=top

The cell contents appear at the top of each cell (the default).

valign=middle

Cell contents are centered vertically in each cell.

valign=bottom

The cell contents appear at the bottom of each cell.

valign=baseline

This is used when you want to ensure that all cells in the row with valign=baseline share the same baseline. This constraint only applies to the first text line for each cell.

Note: In the absence of the VALIGN attribute, the default can be overridden by the presence of a VALIGN attribute on the parent TR element.

NOWRAP

The NOWRAP attribute is used when you don't want the browser to automatically wrap lines. You can then explicitly specify line breaks in paragraphs using the BR element.

AXIS

This defines an abbreviated name for a header cell, which can be used when rendering to speech. It defaults to the cell's content.

AXES

This is a comma separated list of axis names which together identify the row and column headers that pertain to this cell. It is used when rendering to speech to identify the cell's position in the table. If missing the user agent can try to follow up columns and left along rows (right for some languages) to find the corresponding header cells.

Note: a subheader cell may include both attributes - using AXIS to name itself and AXES to name the parent header cell. When data cells refer to header cells with both attributes, the parent header cells are found by following back the head-subhead relationships.