I am trying to create a homepage, which includes hyperlink.
For example, after clicking sth called file1.txt, I should be directed to text file. However, before the file is to be displayed, a box should be popped up asking username and password. Can you tell me how to do it? Thanks.
With plain HTML? You can’t.
The simplest way is to use HTTP Basic Auth. The specifics of which depends on the web server software you use. e.g. for Apache: http://httpd.apache.org/docs/2.2/howto/auth.html