HTML and CSS Reference
In-Depth Information
elements. JavaScript code can be embedded within the HTML elements
of a web page or imported from a separate ile. Not all web pages have
JavaScript components, and users can turn of their browsers' JavaScript
engine if they want to. Robots generally ignore JavaScript code as they
examine web pages.
HTTP (HyperText Transport Protocol)
he set of rules governing
how user agents, web browsers, and the like send requests to a web server
and how the web server responds to the request. he web server returns a
status code and data, or sometimes just the status code, when something
goes wrong. he familiar 404 error code is returned when the web server
cannot ind what you are looking for. here are two primary HTTP
request methods. A
Get
request is typically sent by your browser when
you click a link with the intention of going to another web page. A
Post
request is typically sent when you click a form's submit button, essen-
tially asking that the web server do something with your input.
.
CGI (Common Gateway Interface)
A protocol for dynamically gen-
erating web pages in response to a get request or form submission. he
term is typically used as an adjective to indicate a server-side process,
such as CGI script. CGI programs are typically written using a script-
ing language such as Perl, Ruby, C, vBasic, or Python. Many websites are
entirely driven by CGI processes, although the relative number of such
sites has probably been declining as newer technologies, such as AJAX
and PHP, have become popular.
.
AJAX (Asynchronous JavaScript and XML)
he most recent versions
of JavaScript and other client-side scripting languages contain features
that a developer can use to create web pages that can make independent
HTTP requests to the server while the page is loading or anytime there-
ater. AJAX is the set of techniques used to create web pages with ele-
ments that can be independently updated with new content in response
to a user's mouse click or some other event without having to reload the
entire page. his is how many widgets work.
.
XML (eXtensible Markup Language)
A set of rules for marking up
documents that emphasizes generality and global usability. It is widely
used to transmit arbitrarily structured data in mixed client/server
environments. XML and HTML are compatible members of a family
of markup languages called Standard Generalized Markup Language
(SGML). HTML is an SGML language with a speciic Document Object
.
