To reflect this grouping when the document is rendered, authors can use style sheets to provide borders or change the background color of the bodies. The horizontal alignment of text in all affected cells. There are five possible values case-insensitive :. This attribute has become obsolete in HTML 5 and, therefore, its use is no longer valid. Authors should replace it with style sheet declarations. A caracter that will act as axis for text alignment. It's meant to work together with the align attribute when it has the "char" value.
In other situations it will be completely ignored. This attribute has become obsolete in HTML 5 and its use is consequently invalid. Authors are adviced to replace it with style sheet declarations. An offset, from the first occurrence of the alignment caracter specified in the char attribute and in the direction of the text. Possible values for this attribute are:.
As this attribute is deprecated, use the CSS vertical-align property instead. The table's HTML is shown here. First, the table's overall style attributes are set, configuring the thickness, style, and color of the table's exterior borders and using border-collapse to ensure that the border lines are shared among adjacent cells rather than each having its own borders with space in between. The cells are given a light gray outline which is a single pixel thick, padding is adjusted, and all cells are left-aligned using text-align.
They use a darker background-color , a larger font size, and a thicker, darker bottom border than the other cell borders. Let's see how that's done. Let's take the previous example, add some more students to the list, and update the table so that instead of listing each student's major on every row, the students are grouped by major, with heading rows for each major.
Most of the CSS is unchanged. Row groups convey additional structural information and may be rendered by user agents in ways that emphasize this structure.
When long tables are printed, the head and foot information may be repeated on each page that contains table data. Authors may also group columns to provide additional structural information that may be exploited by user agents. Furthermore, authors may declare column properties at the start of a table definition via the COLGROUP and COL elements in a way that enables user agents to render the table incrementally rather than having to wait for all the table data to arrive before rendering.
Table cells may either contain "header" information see the TH element or "data" see the TD element. Cells may span multiple rows and columns. The HTML 4 table model allows authors to label each cell so that non-visual user agents may more easily communicate heading information about the cell to the user.
Not only do these mechanisms greatly assist users with visual disabilities, they make it possible for multi-modal wireless browsers with limited display capabilities e. Tables should not be used purely as a means to layout document content as this may present problems when rendering to non-visual media. Additionally, when used with graphics, these tables may force users to scroll horizontally to view a table designed on a system with a larger display.
To minimize these problems, authors should use style sheets to control layout rather than tables. This specification includes more detailed information about tables in sections on table design rationale and implementation issues. Here's a simple table that illustrates some of the features of the HTML table model. The following table definition:. The following informative list describes what operations user agents may carry out when rendering a table:.
The HTML table model has been designed so that, with author assistance, user agents may render tables incrementally i. If any of the columns are specified in relative or percentage terms see the section on calculating the width of columns , authors must also specify the width of the table itself. The directionality of a table is either the inherited directionality the default is left-to-right or that specified by the dir attribute for the TABLE element. For a left-to-right table, column zero is on the left side and row zero is at the top.
For a right-to-left table, column zero is on the right side and row zero is at the top. When a user agent allots extra cells to a row see the section on calculating the number of columns in a table , extra row cells are added to the right of the table for left-to-right tables and to the left side for right-to-left tables.
When set for the TABLE element, the dir attribute also affects the direction of text within table cells since the dir attribute is inherited by block-level elements. To specify a right-to-left table, set the dir attribute as follows:. The direction of text in individual cells can be changed by setting the dir attribute in an element that defines the cell.
Please consult the section on bidirectional text for more information on text direction issues. Visual user agents allow sighted people to quickly grasp the structure of the table from the headings as well as the caption. A consequence of this is that captions will often be inadequate as a summary of the purpose and structure of the table from the perspective of people relying on non-visual user agents.
Authors should therefore take care to provide additional information summarizing the purpose and structure of the table using the summary attribute of the TABLE element. This is especially important for tables without captions. Examples below illustrate the use of the summary attribute.
Visual user agents should avoid clipping any part of the table including the caption, unless a means is provided to access all parts, e. We recommend that the caption text be wrapped to the same width as the table. See also the section on recommended layout algorithms. This division enables user agents to support scrolling of table bodies independently of the table head and foot.
When long tables are printed, the table head and foot information may be repeated on each page that contains table data. The table head and table foot should contain information about the table's columns. The table body should contain rows of table data. Each row group must contain at least one row, defined by the TR element.
The following summarizes which tags are required and which may be omitted:. Column groups allow authors to create structural divisions within a table. Authors may highlight this structure through style sheets or HTML attributes e. For an example of the visual presentation of column groups, please consult the sample table. The COL element allows authors to share attributes among several columns without implying any structural grouping. The "span" of the COL element is the number of columns that will share the element's attributes.
This attribute specifies a default width for each column in the current column group. This implies that a column's entire contents must be known before its width may be correctly computed. This attribute is overridden for any column in the column group whose width is specified via a COL element. The number of columns in the column group may be specified in two, mutually exclusive ways:. The advantage of using the span attribute is that authors may group together information about column widths.
Thus, if a table contains forty columns, all of which have a width of 20 pixels, it is easier to write:. When it is necessary to single out a column e. Thus, to apply special style information to the last column of the previous table, we single it out as follows:. The first COL element refers to the first 39 columns doing nothing special to them and the second one assigns an id value to the fortieth column so that style sheets may refer to it.
The table in the following example contains two column groups. The first column group contains 10 columns and the second contains 5 columns. The default width for each column in the first column group is 50 pixels.
The width of each column in the second column group will be the minimum required for that column. The COL element allows authors to group together attribute specifications for table columns. COL elements are empty and serve only as a support for attributes. They may appear inside or outside an explicit column group i. The width attribute for COL refers to the width of each column in the element's span. Once the user agent has calculated the number of columns in the table, it may group them into column groups.
For example, for each of the following tables, the two column calculation methods should result in three columns. The first three tables may be rendered incrementally. However, if the table does not have a fixed width, user agents must receive all table data before they can determine the horizontal space required by the table. Only then may this space be allotted to proportional columns.
If an author specifies no width information for a column, a user agent may not be able to incrementally format the table since it must wait for the entire column of data to arrive in order to allot an appropriate width. If column widths prove to be too narrow for the contents of a particular table cell, user agents may choose to reflow the table.
The table in this example contains six columns. The first one does not belong to an explicit column group. The next three belong to the first explicit column group and the last two belong to the second explicit column group. This table cannot be formatted incrementally since it contains proportional column width specifications and no value for the width attribute for the TABLE element. Once the visual user agent has received the table's data: the available horizontal space will be alloted by the user agent as follows: First the user agent will allot 30 pixels to columns one and two.
Then, the minimal space required for the third column will be reserved. We have set the value of the align attribute in the third column group to "center". All cells in every column in this group will inherit this value, but may override it. In fact, the final COL does just that, by specifying that every cell in the column it governs will be aligned along the ":" character.
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