This silly example tries to open your autoexec.bat file in 3 seconds. No big deal here. ;)

The linking to files on your hard drive can easily be done with browsers.

If you know something like this on a page will load, then either ignore it or simply press the stop button before your page completes loading. Otherwise it is generally harmless or annoying at worst. In this case, instead of making a link to a url, it just links to directories on your hard drive. There is no magic about this, and anyone who's learned a few minutes of how to write html can start doing this too. Note that only you can see the contents of the files displayed (no one else actually sees them). For example:
http://www.fortunecity.com/victorian/hartford/190/drive_scanner.htm