Some history (if you're interested!)
I have tried various methods of maintaining the links to pages on my web site. Initially, all links were relative, not absolute, so I would use:
|<a href="Hello.asp">go to my hello page</a>|
|<a href="http://CoverYourASP.com/Hello.asp">go to my hello page</a>|
This made it easy to move pages between my development server at home and the production server hosted by my ISP.
Unfortunately, I then had a problem with my 404 error handler when some spiders crawled the site. It's a long story, but they would cause the relative links on my pages to be applied from non-existant folders, causing an infinite loop of 404 errors!
So I then "fixed the problem" by using absolute links in the header and footer - no matter how the 404 was generated it would always show spiders the same absolute links.
But that made it difficult to use on my development machine, and yours. All the links in the header and footer pointed to the real CoverYourASP site!
Part 2: Using <base href>...