The target Attribute for the <a> Tag

If you include a target attribute within an <a> tag, the browser will load and display the document named in the tag's href attribute in a frame or window whose name matches the target. If the named frame or window doesn't exist, the browser will open a new window, give it the specified name, and load the new document into that window. Thereafter, hypertext-linked documents that target that name will load into the new window.

Targeted hypertext links makes it easy to create effective navigational tools. A simple table of contents document, for example, might redirect documents into a separate window:

<h3>Table of Contents</h3>
<ul>
  <li><a href="pref.html" target="view_window">Preface</a>
  <li><a href="chap1.html" target="view_window">Chapter 1</a>
  <li><a href="chap2.html" target="view_window">Chapter 2</a>
  <li><a href="chap3.html" target="view_window">Chapter 3</a>
</ul>

The first time the user clicks one of the table of contents hypertext links, the browser will open a new window, name it "view_window," and display the desired document's contents inside it. If the user selects another link from the example table of contents and the "view_window" is still open, the browser will again load the selected document into that window, replacing the previous document.

Throughout the whole process, the window containing the table of contents is accessible to the user. By clicking on a link in one window, the user causes the contents of the other window to change.

Similarly, you can place the table of contents into one frame of a two-frame document and use the adjacent frame for display of the selected documents:

<frameset cols="150,*">
  <frame src="toc.html">
  <frame src="pref.html" name="view_frame">
</frameset>

When the browser initially displays the two frames, the left frame contains the table of contents, and the right frame contains the preface (see Figure 12.6).

When a user selects a link from the table of contents in the left frame (for example, Chapter 1), the browser loads and displays the associated document into the "view_frame" frame on the right side (Figure 12.7). As other links are selected, the right frame's contents change, while the left frame continuously makes the table of contents available to the user.

Special Targets

There are four reserved target names for special document redirection actions:

_blank

The browser always loads a target="_blank" linked document into a newly opened, unnamed window.

_self

This target value is the default for all <a> tags that do not specify a target, causing the target document to be loaded and displayed in the same frame or window as the source document. This target is redundant and unnecessary unless used in combination with the target attribute in the <base> tag in a document's head (see below).

_parent

The _parent target causes the document to be loaded into the parent window or frameset containing the frame containing the hypertext reference. If the reference is in a window or top-level frame, it is equivalent to the target _self.

A brief example may help clarify how this link works. Consider a link in a frame that is part of a three-column frameset. This frameset, in turn, is a row in the top-level frameset being displayed in the browser window. This arrangement is shown in Figure 12.8.

If no target is specified for the hypertext link, it is loaded into the containing frame. If a target of _parent is specified, the document is loaded into the area occupied by the three-column frameset containing the frame that contains the link.

_top

This target causes the document to be loaded into the window containing the hypertext link, replacing any frames currently displayed in the window.

Continuing with the frame hierarchy shown in Figure 12.8, using a target of _top would remove all the contained frames and load the document into the entire browser window.

All four of these names begin with the underscore character. Any other window or target name beginning with an underscore is ignored by the browser. Don't use the underscore as the first character of the name of any frame you define in your documents.

The <base> Default Target

It can be tedious to specify a target for every hypertext link in your documents, especially when most are targeted at the same window or frame. To alleviate this problem, you can add a target attribute to the <base> tag. [the section called "The <base> Header Element"]

The target attribute in the <base> tag sets the default target for every hypertext link in the current document that does not contain an explicit target attribute. For example, in our example table of contents document, almost every link causes the document to be displayed in another window named "view_frame." Rather than include that target in each hypertext link, you should place the common target in the table of contents' <base> tag within its <head>:

<html>
<head>
<title>Table of Contents</title>
<base target="view_frame">
</head>
<body>
<h3>Table of Contents</h3>
<ul>
  <li><a href="pref.html">preface</a>
  <li><a href="chap1.html">chapter 1</a>
  <li><a href="chap2.html" >Chapter 2</a>
  <li><a href="chap3.html">chapter 3</a>
</ul>
</body>
</html>

Notice that we don't include any other target references in the list of hyperlinks, because the browser will load and display all the respective documents in the base target "view_frame."