If you want to send a document to another person via http download,
you can easily do this by giving your file an non-html extension. For
example, if you have a Word Document brochure you wish to give
your visitors access to, instead of coding the hyperlink to a ".doc"
file, you can zip this file and then your HREF tag will automatically
start downloading the file. Just about everyone these days has the
ability to extract zip files, so this is a great tool for letting people
download files from your site that would normally appear in html
format. For example, images, text files and certain Microsoft
application files will display in the visitor's browser, which will be
exactly what you don't want if downloading is your goal.

Using zip files will give your visitors a quick method of retrieving
and storing files from your site. Of course, using this method means
you can add many files to a single zip. You can even zip up your
entire site (great for tutorials and other "how-to" sites) and let your
visitors browse off-line without incurring charges or tying up their
phone lines.