Working with Tables: Module A: Table Basics

Goals To understand how to create basic tables To understand how to use <th> and <caption> elements To understand how to format tables

Creating Basic Tables Tables are collections of rows and columns that you use to organize and display data In a table, the intersection of any given row and column is called a cell

Creating Basic Tables

Creating Basic Tables Tables are also used to lay out Web pages, much like frames have been used The W3C discourages using tables for document layout because tables can be difficult for non-visual user agents to interpret

Creating Basic Tables Additionally, user agents with small monitors, such as Personal Digital Assistants (PDAs), and browsers that use large fonts may have difficulty rendering a Web page that is laid out using tables The W3C encourages the use of Cascading Style Sheets (CSS) for document layout

Basic <table> Elements You create tables using the <table> element Within the <table> element you can nest a number of other elements that specify the content of each cell along with the structure and appearance of the table The <table> element also includes several attributes that affect the appearance and structure of a table

Table Elements

The <td> Element Cells are the most basic parts of a table You create a cell within the <table> element using the <td> element The <td> element stands for “table data” The content of each <td> element is the data that will appear in the table cell

The <td> Element Each <td> element essentially represents a column in the table You declare table cells within table row elements that you create with the <tr> element Each <tr> element you include within a <table> element creates a separate row

Schedule Table

The <th> Element Table cells can contain two types of information: data that you define with the <td> element and heading information that you define with the <th> element

The <th> Element User agents render the content of a <th> element in a distinct manner; most Web browsers display heading information in a bold typeface and align it in the center of the column

Captions and Summaries Most tables include a caption that describes the data in the table You create a caption for a Web page table using the <caption> element

Captions and Summaries The <caption> element must be the first element following the <table> element, and you can include only a single <caption> element per table A caption should provide a short phrase or title that clearly describes the contents of the table

Captions and Summaries The <caption> element is important because it allows non-visual user agents to understand the purpose of a table For short or simple tables, the <caption> element is usually sufficient for describing the purpose of the table

Captions and Summaries For long or complex tables, however, you should also include the summary attribute of the <table> element, which allows you to provide a more detailed summary of a table’s structure and content for use in non-visual user agents

Table Widths You use the width attribute of the <table> element to specify the size of a table You can assign a fixed value in pixels or a percentage representing the visible width of a Web browser window

Table Widths

Horizontal Alignment You can use the align attribute to adjust the horizontal alignment of the contents of all table elements with the exception of the <table> and <caption> elements The values you can assign to the align attribute are left, center, right, and justify

Horizontal Alignment

Structuring Tables Although table structure elements are not required in order for your documents to be well formed, it is a good idea to include them to clearly identify the different parts of your tables

Structuring Tables Table structure elements also allow you to apply default alignment and CSS styles to entire sections of a table and to adjust the width of individual columns

Row Groups You can create table row group elements that consist of a table header, table body, and table footer To define a table header, you use the <thead> element; to define the table body, you use the <tbody> element; and to define the table footer, you use the <tfoot> element

Table Header You must place the <thead> element after any <caption>, <colgroup>, and <col> elements and before the <tbody> and <tfoot> elements Typically, you place table heading information (created with the <th> element) within the <thead> element, as shown on page 229 of the textbook

Table Body The <tbody> element should contain the rows of data that make up the body of a table You can use the <tbody> element to align a table body and to apply CSS formatting to the table body

Table Body You can also include multiple <tbody> elements to control different parts of the table body

Table Footers The <tfoot> element defines information that should be placed at the bottom of a table You use the <tfoot> element to provide additional information about the columns or about the table itself

Table Footers The <tfoot> element must be placed before the <tbody> element in order to allow a user agent to render the structure of the table before it receives the potentially large amount of data that may appear in the table body

Columns There are times when you may want to format the columns in your tables, either individually or as a group In this section you study column groups, which are used for applying default alignment, width, and CSS styles to groups of columns within a table

Column Groups You use the <colgroup> element to create a column group in a table You must place a <colgroup> element after a table’s <caption> element and before its <thead> element

Column Groups The <colgroup> element can be created either as an empty element or as a tag pair that contains <col> elements as its content The empty <col> element allows you to apply formatting to an individual column in a column group

Column Widths You cannot use the <table> element’s width attribute to adjust the size of cells or columns in a table, which are determined automatically by each user agent In addition, you cannot adjust the widths of individual table cells with the <td> and <th> elements

Column Widths However, you can adjust the widths of columns using the width attribute of the <colgroup> or <col> elements

Using Tables to Simulate Frames If you want to use tables to simulate frames, you create a table with the same number of cells as the number of frames you want

Using Tables to Simulate Frames If you want to create two horizontal frames (one at the top of a page and one on bottom), you create a table with two rows, with each row containing a single <td> element Similarly, if you want to create two vertical frames, you create a table with a single row containing two <td> elements

Using Tables to Simulate Frames To create a navigation menu on the left and a content pane on the right, you would place a list of hyperlinks in the left cell and display each link’s associated content in the right cell

Using Tables to Simulate Frames One of the big differences between frames and tables that simulate frames is that when you click a link in a table, the link opens an entirely new page in the same browser window—it does not display a new URL in a different area of the same page as occurs with frames

Formatting Tables You should handle the visual display of content with CSS Nevertheless, you can use several types of built-in table formatting options without CSS, even when using the Strict DTD

Borders You use the <table> element’s border attribute to add a border to a table The value you assign to the border attribute determines the thickness of the border in pixels

Borders

The frame Attribute You can include the frame attribute in the <table> element to specify which sides of the table should display a border

The frame Attribute

Rules You can include the rules attribute in the <table> element to specify which rules should appear in a table

Rules

Displaying Empty Cells Web browsers do not render the borders around empty cells To fix this problem, you need to add a <td> element for each empty cell, and include a non-breaking space character entity ( ) as each cell’s content

Displaying Empty Cells

Cell Margins The cellspacing attribute specifies the amount of horizontal and vertical space between table cells You assign to the cellspacing attribute a value representing the number of pixels that you want between table cells

Cell Margins In comparison, the cellpadding attribute specifies the amount of horizontal and vertical space between each cell’s border and the contents of the cell

Cell Margins

Cells that Span Multiple Rows or Columns You can cause cells to span multiple rows or columns by including the rowspan or colspan attributes in the <td> or <th> elements As an example of the colspan attribute, the table in Figure 6-32 shows a breakdown of the animal kingdom into phylum and class

Cells that Span Multiple Rows or Columns

Vertical Alignment You can use the valign attribute, which adjusts the vertical alignment of the contents of all table elements with the exception of the <table> and <caption> elements The values you can assign to the valign attribute are top, middle (default value), bottom, and baseline

Resources Slides were adapted from the following text & companion lectures: XHTML, Comprehensive First Edition Dan Gosselin Published by Course Technology (2004)

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