HTML and CSS Reference
In-Depth Information
he destination of a link is given by a string of characters called a
Uniform
Resource Locator (URL)
. A special bit of HTML markup, called the anchor
element, makes this portion of text, or that image or those buttons, “active.”
When you click one, your browser requests a new document from the web
server indentiied in the URL.
In addition to links, URLs are used in HTML to load images, video, and
other online media into a page; to apply stylesheets and create pop-up win-
dows; and to specify where form input should be sent. In HTML a URL can
be in partial form, oten called a relative URL. A browser ills in any missing
parts of the URL from the corresponding parts of the current page's URL to
create a full URL. his neat trick makes it easy to relocate a website. A full
URL starts with the protocol to use for the transfer. he URL design is uni-
versal and can reference other Internet things besides Web resources. We will
go into more detail later. For now, suice it to say that the Web's protocol is
HyperText Transport Protocol, abbreviated as “http” or “https” when used in
a URL. he “s” means that a secure (that is, encrypted) connection is made
to the web server so that nobody eavesdropping on the conversation between
your browser and the web server can steal anything important, such as a credit
card number. Otherwise, the https protocol works the same way as http. By
having secure transactions at the protocol level, web page authors and devel-
opers can write HTML that works in either environment.
he web server address comes ater the protocol designation. Following
that, the path to the ile or resource is given. (here's more, but this will do for
now.) hus, when you click a link whose deining anchor element
2
contains a
URL, such as http://www.google.com/about.html, your browser understands
this as a request to open a connection to the Internet server,
www.google.com
,
using the HTTP protocol and to get the resource,
about.html
.
Of course, you do not always have to click a link or button to get somewhere
on the Web. You can just type a portion of a URL into the location window at
the top of your browser, and you are taken there. Alternatively, you can open
an HTML ile from your local computer. (Web developers commonly do this
when working on a website.)
As intelligent as Web browsers currently are, web servers are smarter still. A
single web server can host hundreds of diferent websites, manage many dif-
ferent types of content, read/write information from/to databases, and speak
2.
<a href="http://www.google.com/about.html">About Google</a>
