PHP and MySQL Web Development 4th Ed-tqw-_darksiderg

What Is Ajax?
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display the h1 text however it has been defined—probably with a font size greater than
12pt and with a font-weight value of bold.
In addition to defining selectors, you can also define your own classes and IDs within
a style sheet. Using classes (which can be used on multiple elements in a page) or IDs
(which can be used only once within a page), you can further refine the display and
functionality of elements displayed within your website.This refinement is especially
important in Ajax-enabled sites because you use predefined areas of your document to
display new information retrieved from the remote scripting action.
Classes are defined similarly to selectors—curly braces around the definitions, definitions
separated by semicolons. Following is the definition of a class called ajaxarea:
.ajaxarea {
width: 400px;
height: 400px;
background: #fff;
border: 1px solid #000;
}
In this instance, the ajaxarea class, when applied to a div container, produces a 400-
pixel wide by 400-pixel high square with a white background and a thin black border.
The usage is as follows:
some text
The most common method of using style sheets is to create a separate file with all the
style definitions in it, and then link to it in the head element of your HTML document,
like so:
For more information on CSS, see http://www.w3.org/TR/CSS2/.
Client-Side Programming
Client-side programming occurs within your web browser after a page has been entirely
retrieved from a web server. All the programming functions are included in the data
retrieved from the web server and are waiting to be acted upon. Common actions performed
on the client side include showing or hiding sections of text or images, changing
the color, size, or location of text or images, performing calculations, and validating user
input in a form before sending the form to be processed on the server side.
The most common client-side scripting language is JavaScript—the “J” in Ajax.
VBScript is another example of a client-side scripting language, although it is Microsoftspecific
and thus not a good choice for an open environment in which all manner of
operating systems and web browsers may be in use.