XP

Adding Hypertext Links to a Web Page

XPObjectives

• Create hypertext links between elements within a Web page

• Create hypertext links between Web pages• Review basic Web page structures• Create hypertext links to Web pages on the Internet• Distinguish between and be able to use absolute and

relative pathnames• Create hypertext links to various Internet resources,

including FTP servers and newsgroups

XPCreating a Hypertext Document

• Hypertext documents contain hypertext links, items that you can select to view another topic or document, often called the destination of the link.

• These links can point to:– another section

– the same document

– to a different document

– to a different Web page

– to a variety of other Web objects

XPCreating Anchors

• The <a> tag creates an anchor, text that is specially marked so that you can link to it from other points in a document.

• Text that is anchored is the destination of a link; it is not the text you click on.

• Each anchor has its own anchor name, using the “name” attribute i.e. <a name=“cc”>Classes</a>.

• An anchor doesn’t have to be text. You can mark an inline image as an anchor.

• Adding an anchor does not change your document’s appearance in any way. It merely creates locations in your Web page that become destinations of links.

XPCreating Links

• To create a link to an anchor, use the same <a> tag you used to create the anchor.

• The <a> tags used to create links are sometimes called link tags.

• Use the href attribute, which is short for Hypertext Reference, to indicate the location to jump to.– href can refer to an anchor that you place in the document or to a

different Web page or a resource anywhere on the Internet– it is important to note that the href attribute is case sensitive

• You link to an anchor using the anchor name preceded by a pound (#) symbol i.e. <a href=“#gra”>Grading</a>.

XPWeb Page Structures

• Storyboarding your Web pages before you create links helps you determine which structure works best for the type of information you’re presenting.

• You want to ensure that readers can navigate easily from page to page without getting lost.

• You’ll encounter several Web structures as you navigate the Web.

• Examining some of these structures can help you decide how to design your own system of Web pages.

XPLinear Structures

In this structure you can jump only from one page to the next or previous page

Link to previous page

Link to next page

This figure shows one common Web page structure, the linear structure, in which each page is linked to the next and to previous page, in an ordered chain of pages.

XPAugmented Linear Structure

This figure shows an augmented linear structure, in which you include a link in each page that jumps directly back to the first page, while keeping the links that allow you

to move to the next and previous pages.

first link jumps to previous page

second link jumps back to beginning

third page has three links

third link jumps to next page

XPHierarchical Structure

XPCombination of Linear and Hierarchical Structures

This figure shows a hierarchical structure in which each level of pages is related in a linear structure.

information about the play

the scenes

each level is linear

information about the acts

over

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is h

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XPWeb Structures Continued

• A little foresight can go a long way toward making your Web pages easier to use.

• The best time to organize a structure is when you first start creating pages, when those pages are small in number and more easily managed.

• If you’re not careful, your structure can become confusing and unmanageable for the user.

XPLinking to a Document

• To create a link to a document, use the same <a> tag with the href attribute i.e. <a href=“contact.htm”>Contact me</a>.

• In order for the browser to be able to locate and open contact.htm, it must be in the same folder as the document containing the link.

XPLinking to a Section of a Document

• To navigate to a specific location elsewhere in a document, rather than the top, you can set anchors and link to an anchor you create within the document.– for example, to create a link to a section in the Web page

home.htm marked with an anchor name of “interests,” you create an anchor in home.htm in the section on Interests, and then enter the following HTML code in the current document:<a href=“home.htm#interests”> View my interests </a>• the entire text, “View my interests,” is linked to the Interests section in the

home.htm file, via the anchor name “interests”

• the pound symbol (#) in this tag distinguishes the filename from the anchor name

XPLinking to Documents in Other Folders

• Browsers assume that if no folder information is given, the file is in the same folder as the current document.

• When referencing a file located in a different folder than the link tag, you must include the location, or path, for the file.

• HTML supports two kinds of paths: absolute paths and relative paths.

XPAbsolute Pathnames

• An absolute pathname provides a precise location for a file.• With HTML, absolute pathnames begin with a slash (/) and

are followed by a sequence of folders beginning with the highest level folder and proceeding to the folder that contains the file.

• Each folder is separated by a slash.• After you type the name of the folder or folders that contains

the file, type a final slash and then the filename itself i.e. /tutorial.02/case/parks.htm.

• HTML also requires you to include the drive letter followed by a vertical bar (|) i.e. /C|/tutorial.02/case/parks.htm.

XPRelative Pathnames

• A relative path specifies the location for a file in relation to the folder containing the current Web document.

• As with absolute pathnames, folder names are separated by slashes.

• Unlike absolute pathnames, a relative pathname does not begin with a slash.

• To reference a file in a folder directly above the current folder in the folder hierarchy, relative pathnames use two periods (..) i.e. ../tutorial/chem.htm.

XPRelative Pathnames Continued

• Relative pathnames make your hypertext links portable.

• Unlike absolute pathnames, If you move your files to a different computer or server, the hypertext links will stay intact.

• If absolute pathnames are used, each link has to be revised. This can be a very tedious process.

XPLinking to Documents on the Internet

• To create a hypertext link to a document on the Internet, you need to know its URL.

• A URL, or Uniform Resource Locator, specifies a precise location on the Web for a file.

• You can find the URL of a Web page in the Location or Address box of your browser’s document window.

• Once you know a document’s URL, you can create a link to it by adding the URL to the <a> tag along with the href attribute in your text file i.e. <a href http://www.mwu.edu/course/info.html>Course Information</a>.

XPUniform Resource Locator (URL)

• Each URL follows the same format.– The first portion of the URL identifies the

communication protocol, which is a set of rules that governs how information is exchanged.

– Web pages use the communication protocol HTTP, short for Hypertext Transfer Protocol, so all Web page URLs begin with the letters “http”.

– Following the communication protocol, there is typically a separator, such as a colon and two slashes (://) i.e. http://www.mwu.edu.

XPInterpreting Parts of a Uniform Resource Locator (URL)

This figure interprets a Web page with the URL http://www.mwu.edu/course/info.html#majors.

XPDisplaying Linked Documents in a New Window

• By default, each Web page you open is displayed in the main browser window, replacing the one you were viewing last.

• To force a document to appear in a new window, instead of the main browser window, you would use the target attribute in the href tag i.e. <a href=“url” target=“new_window”>Hypertext</a>– url is the URL of the page, and new_window is a name assigned to the

new browser window

– the value use for the target attribute is used by the browser to identify the different open windows in the current browser session

XPExternal Hyperlinks

• You can set up external hyperlinks to open in the same browser window by using the same value for the target attribute.– if you do, the first hyperlink clicked opens the new window and displays

the contents of the external file

– as subsequent external hyperlinks are clicked, they replace the contents of the already opened window, and the contents of the main browser window remain unaffected

• If you want your external documents to be displayed in their own browser window, you can assign a unique target value for each hyperlink, or you can assign the _blank keyword to the target attribute i.e. <a href=“url” target=_blank>Hypertext</a>.

XPLinking to File Transfer Protocol (FTP) Servers

• You can create links to other Internet resources, such as FTP (File Transfer Protocol) servers.– FTP servers can store files that Internet users can

download, or transfer, to their computers– FTP is the communications protocol these file servers

use to transfer information– URLs for FTP servers follow the same format as those

for Web pages, except that they use the FTP protocol rather than the HTTP protocol i.e. <a href= ftp://ftp.microsoft.com>Microsoft FTP server</a>.

XPLinking to Usenet News

• Usenet is a collection of discussion forums called newsgroups that let users exchange messages with other users on a wide variety of topics.

• The URL for a newsgroup is news:newsgroup. • To access the surfing newsgroup alt.surfing, you

place this line in your HTML file i.e. <a href=news:alt.surfing>Go to the surfing newsgroup</a>.

XPLinking to E-mail

• Many Web designers include their e-mail addresses on their Web pages, so that users who access the page can send feedback.

• You can identify e-mail addresses as hypertext links.– when a user clicks the e-mail address, the browser starts a mail

program and automatically inserts the e-mail address into the “To” field of the outgoing message

• The URL for an e-mail address is mailto:e-mail_address.• To create a link to the e-mail address davis@mwu.edu, the

following code would be entered <a href=mailto:davis@mwu.edu>davis@mwu.edu</a>