Sometimes when you click on a link to download a file, you will see a dialog box like the following.

This box tells you that your browser doesn't know what to do with the file you are about to download. Web browsers have a very useful feature that makes downloading easy: applications can be configured to start automatically when you download a certain kind of file. For instance, when you download a sound file, your browser can automatically start a sound application (if you have one installed) and play the file. You won't have to worry about starting your sound application yourself, and then looking for the sound file on your hard drive. An application that is used in this way is called a Helper Application.

Helper Applications also work with received e-mail attachments as well as files downloaded from a Web page.

NOTE: If you are worried about viruses, you should not configure your browser to start Helper Applications automatically. You should save the file to your hard drive first, then check it with virus checking software.

To find out how to configure your browser to start Helper Applications automatically, choose your browser and operating system:

Windows (95 and 3.11): Netscape Communicator 4

Macintosh: Netscape Communicator 4

Related questions:

How do I download things from the Internet?
What do the different actions in the Helpers window mean?
What is a MIME type?