HTML and CSS Reference
In-Depth Information
to use symbolic links on the Web server to reference one copy of the file from multiple
locations. However, because HTML is the subject here, we focus on the former solution
using the
base
element.
The
base
element defines the base for all relative URLs within a document. Setting the
href
attribute of this element to a fully qualified URL enables all other relative references to
use the defined base. For example, if
<base>
is set as
<base href="http://www.htmlref
.com/">
, then all the anchors in the document that aren't fully qualified will prefix http://
www.htmlref.com/ to the destination URL. Because
base
is an empty element, it would have
to be written as
<base href="http://www.htmlref.com/" />
to be XHTML-compliant.
A simple example is presented here:
<!DOCTYPE html>
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=utf-8">
<title>
Base URL
Example
</title>
<base href="http://htmlref.com/">
</head>
<body>
<ul>
<li><a href="AppD/basiclink.html">
Basic linking example
</a></li>
<li><a href="AppD/base.html">
Base example
</a></li>
<li><a href=".">
Book Site Home Page
</a></li>
<li><a href="http://htmlref.com">
Book Site Home Page Alternate
</a></li>
<li><a href="http://www.google.com">
Google
</a></li>
</ul>
</body>
</html>
O
NLINE
http://htmlref.com/AppD/base.html
It is most interesting to run this example from another server or locally off your disk, as you
will note that the relative URLs will resolve to the topic support site per the address in the
<base>
tag.
Since a
<base>
tag can occur only once in an HTML document—within the
head
element—creating sections of a document with different base URL values is impossible.
Such a feature might someday be added to a sectioning element, but until then, HTML
authors have to deal with the fact that shorthand notation is useful only in some places. See
the entry in Chapter 3 for more information on the
<base>
tag.
URL Challenges
While we all know and use URLs, we don't necessarily understand all their little quirks. We
enumerate a few of the more common challenges faced when working with URLs here.
