New Perspectives on Creating Web Pages with HTML Adding Hypertext Links to a Web Page 1
Objectives 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 2
Creating 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 on the same document to a different document to a different Web page to a variety of other Web objects 3
Opening A Web Page This figure shows that a browser may only show a portion of the web page. The user must scroll down to see the rest of the web page. vertical scroll bar horizontal scroll bar can also be shown 4
Adding Hypertext Links You can place hypertext links at the top of a web page to make it easier for the user to navigate to a particular section of the document instead of scrolling. 5
Creating 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. 6
Creating Anchors Internal hyperlinks required two steps: Enter an anchor tag using a # before the name of the target location. Define where the link will take you (the target location) with the NAME attribute. <HTML> <TITLE>Text</TITLE> <BODY> <A HREF= #POWERFUL > Powerful Lines</A> <P>Text</P> <P>Text</P> <P>Text</P> <A NAME= POWERFUL > Powerful Lines</A> </BODY> </HTML> 7
Hyperlinks Inside Your Document Internal hyperlinks jump from an index to content below, in another spot on a Web page. Internal hyperlink Jumps to content below 8
How an Anchor Works hypertext links When the user clicks one of the hypertext links, the link will go directly to that section (anchor, which is the destination of the link) within the web page. anchor 9
Creating 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>. 10
Creating Links Continued After you create the anchors that serve as destinations for your links, you need to create the links themselves. You should be careful to make each anchor name unique within a document. The <a> tag you use to create the anchor and the href attribute to indicate the location to jump to. 11
Text Links in the Browser If the headings do not appear as text links, check your code to make sure that you are using the <a> and </a> tags around the appropriate text, the href attribute within the tag, and the quotes and # symbols. Text formatted as links 12
Web 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. 13
Linear Structures 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. Link to previous page In this structure you can jump only from one page to the next or previous page Link to next page 14
Augmented 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 15
Hierarchical Structure This figure shows the hierarchical structure, which starts with a general topic that includes links to more specific topics. Each specific topic includes links to yet more specialized topics, and so on. In a hierarchical structure, users can move easily from general to specific and back, but not from specific to specific. 16
Hierarchical Structure on AltaVista Web Page As with the linear structure, including a link to the top of the structure on each page gives users an easy path back to the beginning. Subject catalogs such as the AltaVista directory of Web pages often use this structure. This figure shows this site, located at http://www.altavista.com. 17
Combination of Linear and Hierarchical Structures This figure shows a hierarchical structure in which each level of pages is related in a linear structure. overall structure is hierarchical information about the play each level is linear information about the acts the scenes 18
Web 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. 19
Multipage Document with No Coherent Structure This structure is confusing, and it makes it difficult for readers to grasp the contents of the overall Web site. Moreover, a user who enters this structure at a certain page might not be aware of the presence of the other pages. 20
Creating Links Among Documents Unlike creating hypertext links between elements on the same page, this process does not require you to set an anchor in a file to link to it; the filename serves as the anchor or destination point. links to the conttxt.htm document, which contains contact information the chem.htm document, which is the document containing the links. links to the linktxt.htm document, which contains links to various Chemistry Web sites. 21
Linking 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. 22
HTML Code that Links to Other Documents <a> tags to point to other documents 23
Browser Displaying Links to Other Documents links to the Contact and Links page 24
Linking 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 25
Adding Links to Specific Locations in a Page The pound symbol (#) in these tags (shown in red) distinguishes the filename from the anchor name. 26
Links in the Chemistry Page that Point to Anchors in the Links Page links 27
Linking 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. 28
Absolute 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. 29
Folder Tree This figure shows five HTML files that are located in four different folders. The top most folder is the tutorial.02 folder. Within the tutorial.02 folder are the tutorial and case1 folders, and within the case1 folder is the extra folder. 30
Absolute Pathname This figure shows absolute pathnames for five HTML files. 31
Relative 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. 32
Relative 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. 33
Relative Pathnames This figure shows the relative pathnames and their interpretations for HMTL files and how they would be displayed. 34
Linking 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 35 Information</a>.
Uniform 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. 36
Interpreting Parts of a Uniform Resource Locator (URL) This figure interprets a Web page with the URL http://www.mwu.edu/course/info.html#majors. 37
Link to Another Page on the Web As long as your computer is connected to the Internet, clicking the text within the tag navigates you to the document located at the specified URL. Links to the College Board AP Internet page 38
College Board AP Page Chemistry page remains open in the original browser window AP page in a separate browser window 39
Displaying 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 40
External 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>. 41
Linking 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>. 42
Displaying a FTP Site Different browsers can display the contents of an FTP site in different ways. This figure shows what it might look like with Internet Explorer. 43
Linking 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>. 44
Accessing the alt.surfing Newsgroup When you click a link to a newsgroup, your computer starts your newsgroup software and accesses the newsgroup. This figure shows an example of the Outlook Newsreader program. 45
Linking 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> 46
Mail Message Window window opens when the davis@mwu.edu link is clicked 47
Adding an Email Link the address itself is in the code for the mailto: URL mail message window opens with e-mail address already inserted 48
Coloring Text You will use three separate attributes to color text : Use the text attribute to change color of text Use the hypertext link color attribute to change color of hypertext links Use the visited link attribute to change color of hypertext links that have been selected <HTML> <TITLE>Text</TITLE> <BODY TEXT=BLUE LINK=RED VLINK=GREEN> <P>Text</P> <P>Text</P> <P>Text</P> </BODY> </HTML> 49
Coloring Text <HTML> <TITLE>Text</TITLE> <BODY TEXT=BLUE LINK=RED VLINK=GREEN> <P>Text</P> <P>Text</P> <P>Text</P> </BODY> </HTML> 50
Summary Learned how to work with hypertext links. Learned how to create anchors within a Web page. Created links to anchors. Created hyperlinks within a single document and links to other Web pages. Discussed creating hyperlinks to resources other than Web pages, such as FTP sites, e-mail addresses and Gopher servers. 51