Internet Explorer 7 and Firefox 2 Features
A web browser is software that allows the user to view certain types of Internet files in an interactive environment. Figure 2.1 shows the Deitel Home Page using Internet Explorer 7 web browser, and Fig. 2.2 uses Firefox 2. The URL (Uniform Resource Locator) http://www.deitel.com is found in the Address bar in IE7, and the Location bar in FF2.
The URL specifies the address (i.e., location) of the web page displayed in the browser window. Each web page on the Internet is associated with a unique URL. URLs usually begin with http://, which stands for Hypertext Transfer Protocol (HTTP), the standard protocol (or set of communication rules) for transferring web documents over the Inter-net. URLs of websites that handle private information, such as credit card numbers, often
begin with https://, the abbreviation for Hypertext Transfer Protocol over Secure Sockets Layer (HTTPS), the standard for transferring encrypted data on the web.
There are several techniques for navigating between URLs. You can click the Address field and type a web page’s URL, then press Enter or click Go (in IE7, this is the same button as Refresh) to request the web page located at that URL. For example, to visit Yahoo!’s website, type www.yahoo.com in the Address bar and press the Enter key. Clicking Refresh loads the latest version of the web page from the current website. IE7 and FF2, as well as most other popular browsers, add the http:// prefix to the website name because HTTP is the default protocol used for the web.
Another way to navigate the web is via visual elements on web pages called hyperlinks that, when clicked, load a specified web document. Both images and text may be hyperlinked. When the mouse pointer hovers over a hyperlink, the default arrow pointer changes into a hand with the index finger pointing upward. Often hyperlinked text appears underlined and as in different color from regular text in a web page. Originally used as a publishing tool for scientific research, hyperlinks are widely used to reference sources, or sites that have more information on a particular topic. The paths created by hyperlinking create the effect of the “web.”
Hyperlinks can reference other web pages, e-mail addresses, files and more. If a hyper-link’s URL is in the form mailto:emailAddress, clicking the link loads your default e-mail program and opens a message window addressed to the specified e-mail address. Note that these hyperlinks are generally displayed on the screen as just the e-mail address or the recipient’s name.
If a hyperlink references a file that the browser is incapable of displaying, the browser prepares to download the file, and generally prompts the user for information about how the file should be stored. When a file is downloaded, it is copied onto the user’s computer. Programs, documents, images and sound files are all examples of downloadable files.
Many browsers, including IE7 and FF2, provide tabbed browsing. Holding down the Ctrl key and pressing the letter T while in the IE7 or FF2 browser opens another tab in the same window, allowing the user to browse multiple pages without cluttering the desktop with many windows. [Note: For Mac users, all references to the Ctrl key in this chapter’s shortcuts should be replaced with the Command key.] Also, pressing Ctrl while clicking a link will open the requested page in a new tab. Clicking on the tabs switches between the different pages in the browser, and web pages are then accessed normally. Using tabs is an excellent way to keep the browser organized when viewing multiple pages at once.
Using the History Feature
IE7 and FF2 maintain a History list of previously visited URLs in chronological order. This feature allows users to return to recently visited websites easily. The history feature can be accessed several different ways. The simplest and most frequently used method is to click the Forward and Back buttons located at the top of the browser window (see Fig. 2.1). The Back button reloads into the browser the page you last visited. Assuming that you used the Back button to view previously visited pages, the Forward button would load the next URL from the history into the browser. The keyboard shortcut for Forward is <Alt> and the Right Arrow key or just Shift and Backspace, and the shortcut for Back is <Alt> and the Left Arrow key or simply Backspace.
In IE7, the user can view the last and next nine web pages visited and the current page by clicking the down arrows immediately to the right of the Forward button; the user can then request one of the recently viewed pages by clicking the title of the page in the drop-down list. In FF2, there are separate menus to the right of both the Forward and the Back buttons. Each displays the previous and following fifteen pages in the history, respectively. Note that these methods only display history results from the browser’s current session, which is the period when the browser remains open. In IE7 and FF2, there is a menu to the right of the address bar which displays a longer but more basic history of visited sites (it does not include any URLs accessed through hyperlinks), including websites that were visited in previous sessions. Another way to display sites from a previous session is to use
Selecting History from the down-arrow menu in IE7, or clicking the History menu, then the Show In Sidebar option in FF2, divides the browser window into two sections: the History window (on the left) and the content window (Figs. 2.3–2.4). In IE7, clicking the yellow star icon in the upper left of the window, then selecting the History option, dis-plays a similar menu. By default, the History window lists the URLs visited in the past twenty days in IE7 and nine days in FF2.
The History window contains heading levels ordered chronologically. Within each time frame (e.g., Today) headings are alphabetized by website name (although the organi-zation can be changed clicking the History drop-down menu in IE7 or the View drop-down menu of FF2, both located in the History window). This window is useful for finding pre-viously visited websites without having to remember the exact URL. Selecting a URL from the History window loads the web page into the content window.
URLs from the history can be displayed in a drop-down list when a user types a URL into the Address bar. This feature is called AutoComplete. Any URL from this drop-down list can be selected with the mouse to load the web page at that URL into the browser (Fig. 2.5).
For some users, such as those with dial-up connections, maintaining a connection for long periods of time may not be practical. For this reason, web pages can be saved directly to the computer’s hard drive for off-line browsing (i.e., browsing while not connected to the Internet). Select Save As… in IE7, or Save Page As… in FF2, both from the File menu to save a web page and all its components, including the images. [Note: To display the File menu in IE7, press the Alt key.] This option is also available under the Page menu in IE7 (Fig. 2.1). Individual images from a website can also be saved by clicking the image with the right mouse button and selecting Save Picture As… (IE7) or Save Image As... (FF2) from the displayed context menu (Fig. 2.6).
As mentioned earlier, files from the Internet may be copied to a computer’s hard drive by a process called downloading. This section discusses the types of documents commonly downloaded from the Internet and techniques for downloading them. [Note: You should always be cautious when downloading files from the Internet, as they may contain viruses. Only download from sites that you trust.]
Some common Internet downloads are applications (i.e., software that performs spe-cific functions, such as word processing), plug-ins and extensions. Plug-ins are specialized pieces of software that help the browser support additional content types. An example of an IE7 and FF2 plug-in is the Acrobat Reader from Adobe, Inc. (www.adobe.com/products/acrobat/readstep2.html), which allows users to view PDF (Portable Docu ment Format) documents that otherwise cannot be rendered by the browser. Another popular plug-in allows the browser to render Flash content, which adds audio, video and animation effects to a website. To view sites enabled with Flash, download the Adobe Flash Player plug-in at www.adobe.com/products/flashplayer. Microsoft’s rich media plug-in, Silverlight, is available for download at silverlight.net/GetStarted. (Both
Flash and Silverlight are discussed in much greater depth in Chapters 16, 17 and 19). Nor-mally the browser prompts the user to download a plug-in when one is needed. Plug-ins may also be downloaded from CNET (www.download.com). This site has a large, search-able index and database of many plug-in programs available for download.
Extensions are add-ons that enhance the preexisting functionality of the browser. Examples of extensions include blog editors, universal uploaders and various translation dictionaries and tools. Many IE7 add-ons can be found at www.ieaddons.com, and FF2 add-ons can be browsed and downloaded at https://addons.mozilla.org.
Viewing Source Code
Clicking on the View menu followed by the Source option in IE7 and Page Source in FF2 allows you to view the source code, or the original code written to create the web page you are viewing. Generally, source code is easy for humans to read and interpret, and allows the viewer to understand how the programmer created the page. For example, if an ele-ment of a web page does not display properly, examining the source code can help to in-form the user what the programmer was trying to do. Examining source code is a useful tool for debugging your own code, or for learning how web developers create some of the elements you see on the web.
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