Links

If you've ever done any Web page design or programming,
you're undoubtedly familiar with the structure of a link in HTML. In technical
terms, an HTML link uses the anchor element (whose starting and ending tags are
<a> and </a>), and
one of its main attributes, href, which has a URL as
its value. Text or images placed inside the beginning and ending <a> tags make a link that, when clicked, goes to the
URL in the href attribute, like this:

<a href="http://www.myplace.com">Click Here</a>

So clicking a link is one form of user interaction enabling
you to communicate with the server. But it's pretty limited, because all you can
do is make a request for the page that's already supplied by the site designer.
For example, if I click a link to the About page, the only reason it goes to the
right page is because the site designer has already hard-coded the link with the
URL for that page.