Many file types are available on the Internet. In addition to HTML, JSP, GIF, JPEG, and other files that are used to present a Web page, there are graphics, movies, sounds, and many other file types you can open and view. Internet Explorer can't work with all these file types directly, and fortunately, it doesn't have to. Internet Explorer and other Web browsers use plug-ins and helper applications to expand their capabilities so that they can work with files that they don't natively support.
Plug-ins are software that can be incorporated into a Web browser when it opens (thus, the term plug-in). Internet plug-ins enable applications to display files that are of the specific types handled by those plug-ins. For example, the QuickTime plug-in enables Web browsers to display QuickTime movies.
As you travel around the Web, you might encounter file types for which you do not have the required plug-in. In that case, you need to find and install the plug-in you need. Usually, sites will have links to places from which you can download the plug-ins needed for the file types on the site. There are a couple of places in the system where plug-ins can be stored.
Plug-ins that are available to all user accounts are stored in the folder Mac OS X/Library/Internet Plug-Ins/, where Mac OS X is the name of your startup volume.
You must be logged in under an Administrator account to be able to store a plug-in in this directory.
Internet plug-ins can also be stored in a specific user account, in which case they are available only to that user. A user's specific plug-ins are in the location shortusername/Library/Internet Plug-Ins/, where shortusername is the short name for the user account.
To install a plug-in, simply place it in the directory that is appropriate for that plug-in (to be available either to all users or to only a specific user). Quit the Web browser and then launch it again to make the plug-in active.
Some plug-ins are installed using an installer application, in which case you don't need to install the plug-in manually.
If you open the Internet Plug-Ins directories, you will see the plug-ins that are currently installed. Any plug-in installed in this folder can be used by a supported Web browser.
Many plug-ins are available for Web browsers. The QuickTime plug-in is installed by default so that you can view QuickTime movies in Web browsers. Additionally, the Shockwave Flash plug-in is installed by default as is the Java Applet plug-in. There are many other plug-ins you might want to download and install.
When you attempt to view a file for which you do not have the appropriate plug-in, you will see a warning dialog box that tells you what to do. Usually, you see instructions to help you find, download, and install the plug-in as well.
After a plug-in is installed in the appropriate folder, it works with a Web browser to provide its capabilities. When you click a file that requires the plug-in to be used, the appropriate plug-in activates and enables you to do whatever it is designed to do. For example, when you open a QuickTime movie, you see the controls that enable you to watch that movie within the Web browser.
Although plug-ins provide additional capability by "plugging in" to a Web browser, helper applications are standalone applications that Web browsers can use to work with files of specific types. Any application on your Mac can be used as a helper application.
Web browsers maintain a list of document types for which helper applications should be used. When you open a file type that has a helper application, that application opens and you can use it to work with a file. Web browsers have a default helper application list that links helper applications to many different document types. You can add, change, or delete file types and applications from this list.
For example, in the previous section, you learned how StuffIt Expander can decode and uncompress files you download from the Internet. StuffIt Expander is a helper application; as you saw earlier, you can also use the application independently of a browser. When a browser opens a file type for which StuffIt Expander is the designated helper application, the browser opens StuffIt Expander and "passes" the file to it for processing.
Using helper applications is just like using those applications as standalone applications (after the browser opens the application and passes a file to it). For example, suppose that the application Microsoft Word is the designated helper application for files with the .doc file extension. When you click a file whose name ends in .doc, the browser launches Word and passes the document file to it. The document opens in Word and you can work with it just as you can any other Word document.
Using helper applications is simple, but determining which helper applications are used can be a bit more difficult. You need to be able to relate specific file extensions to the application you want to use as the helper application for that file type.
The best way to see how this works is to work through an example. In this example, the application StuffIt Expander will be designated as the helper application for Zip files you download. This means that when you download a Zip file, StuffIt Expander will be opened and will unzip the file automatically.
By default, Internet Explorer already uses StuffIt Expander as the file helper associated with Zip files. However, this example provides steps that are typical when you need to associate a file with a file helper and so is a worthwhile exercise.
Open the Internet Explorer Preferences window and click File Helpers to open the File Helpers Settings pane. This pane provides a list of applications along with their descriptions. Next to each, you will see the filename extension and MIME file type of the files for which that application is the helper.
Click Add and the Edit File Helper window opens. This window provides the controls and fields you need to designate a helper application for any file type. The window will be empty when you create an association.
Describe the association you are creating.
In the example, I used "Zip files."
Press Tab and enter the extension for the file type for which you are creating an association.
In this example, I entered ".zip" as the extension.
In the MIME type field, enter application/zip.
Enter the four-letter file type and creator codes for the files you will be associating with this application.
In the example, I entered "ZIP " in both places (the letters "ZIP" followed by a space).
Explaining MIME, file types, and file creators is beyond what I have room to cover here. Usually, you can find what you need to enter by looking at one of the existing associations. In fact, that will often work for any new association you want to create. Use the existing associations as guides.
Using the How to Handle pop-up menu, choose how you want these files to be handled.
Because I want the files to be processed with the application (rather than being viewed, for example), I chose Post-Process with Application.
Use the Open dialog box to choose the application that you want to be the helper application for files of this type.
In the example, I selected StuffIt Expander.
Click OK to return to the File Helper Settings pane and you will see your new association in the window.
You can change any existing helper application association, such as changing the help application that is used for a specific file type, by selecting it and clicking Change. Edit the settings in the window and click OK. Later in this chapter, you will see how to change the helper application for files you download from FTP sites.
After this, whenever you open a file of the type for which you created an association, Internet Explorer will automatically use the helper application you specified.