HTML Links

2018-07-03 本文已影响11人春暖花开奇奇乐乐

Note: A link does not have to be text. It can be an image or any other HTML element.

Syntax

In HTML, links are defined with the <a> tag:
<a href="url">link text</a>

Web Links

Example: <a href="https://www.w3schools.com/html/">Visit our HTML tutorial</a>

Note: Without a forward slash at the end of subfolder addresses, you might generate two requests to the server. Many servers will automatically add a forward slash to the end of the address, and then create a new request.

Local Links

The example above used an absolute URL (a full web address).

A local link (link to the same web site) is specified with a relative URL (without http://www....).

<a href="html_images.asp">HTML Images</a>

HTML Link Colors

By default, a link will appear like this (in all browsers):

An unvisited link is underlined and blue
A visited link is underlined and purple
An active link is underlined and red
You can change the default colors, by using CSS:

<!DOCTYPE html>
<html>
<head>
<style>
a:link {
    color: green;
    background-color: transparent;
    text-decoration: none;
}
a:visited {
    color: pink;
    background-color: transparent;
    text-decoration: none;
}
a:hover {
    color: red;
    background-color: transparent;
    text-decoration: underline;
}
a:active {
    color: yellow;
    background-color: transparent;
    text-decoration: underline;
}
</style>
</head>
<body>

<h2>Link Colors</h2>

<p>You can change the default colors of links</p>

<a href="html_images.asp" target="_blank">HTML Images</a> 

</body>
</html>

HTML Links - The target Attribute

The target attribute specifies where to open the linked document.

The target attribute can have one of the following values:

_blank - Opens the linked document in a new window or tab
_self - Opens the linked document in the same window/tab as it was clicked (this is default)
_parent - Opens the linked document in the parent frame
_top - Opens the linked document in the full body of the window
framename - Opens the linked document in a named frame

This example will open the linked document in a new browser window/tab:
<a href="https://www.w3schools.com/" target="_blank">Visit W3Schools!</a>

Tip: If your webpage is locked in a frame, you can use target="_top" to break out of the frame: <a href="https://www.w3schools.com/html/" target="_top">HTML5 tutorial!</a>

HTML Links - Image as Link

It is common to use images as links:

<a href="default.asp">
  <img src="smiley.gif" alt="HTML tutorial" style="width:42px;height:42px;border:0;">
</a>

Note: border:0; is added to prevent IE9 (and earlier) from displaying a border around the image (when the image is a link).

Link Titles

The title attribute specifies extra information about an element. The information is most often shown as a tooltip text when the mouse moves over the element.

<a href="https://www.w3schools.com/html/" title="Go to W3Schools HTML section">Visit our HTML Tutorial</a>

HTML Links - Create a Bookmark

HTML bookmarks are used to allow readers to jump to specific parts of a Web page.

Bookmarks can be useful if your webpage is very long.

To make a bookmark, you must first create the bookmark, and then add a link to it.

When the link is clicked, the page will scroll to the location with the bookmark.

First, create a bookmark with the id attribute:
<h2 id="C4">Chapter 4</h2>

Then, add a link to the bookmark ("Jump to Chapter 4"), from within the same page:
<a href="#C4">Jump to Chapter 4</a>

Or, add a link to the bookmark ("Jump to Chapter 4"), from another page:
<a href="html_demo.html#C4">Jump to Chapter 4</a>

External Paths

External pages can be referenced with a full URL or with a path relative to the current web page.

This example uses a full URL to link to a web page:
<a href="https://www.w3schools.com/html/default.asp">HTML tutorial</a>

This example links to a page located in the html folder on the current web site:
<a href="/html/default.asp">HTML tutorial</a>

This example links to a page located in the same folder as the current page:
<a href="default.asp">HTML tutorial</a>

Chapter Summary

Use the <a> element to define a link
Use the href attribute to define the link address
Use the target attribute to define where to open the linked document
Use the <img> element (inside <a>) to use an image as a link
Use the id attribute (id="value") to define bookmarks in a page
Use the href attribute (href="#value") to link to the bookmark