Adobe Dreamweaver CC 2015 - Manual (Page 156)

149
Layout and design
Last updated 6/3/2015
Apply the Set Nav Bar Image behavior
Apply the Jump Menu behavior
Laying out pages with CSS
About CSS page layout
A CSS page layout uses the Cascading Style Sheets format, rather than traditional HTML tables or frames, to organize
the content on a web page. The basic building block of the CSS layout is the div tag—an HTML tag that in most cases
acts as a container for text, images, and other page elements. When you create a CSS layout, you place div tags on the
page, add content to them, and position them in various places. Unlike table cells, which are restricted to existing
somewhere within the rows and columns of a table, div tags can appear anywhere on a web page. You can position div
tags absolutely (by specifying x and y coordinates), or relatively (by specifying its location with respect to its current
location). You can also position div tags by specifying floats, paddings, and margins—the preferred method by today’s
web standards.
Creating CSS layouts from scratch can be difficult because there are so many ways to do it. You can create a simple two-
column CSS layout by setting floats, margins, paddings, and other CSS properties in a nearly infinite number of
combinations. Additionally, the problem of cross-browser rendering causes certain CSS layouts to display properly in
some browsers, and display improperly in others. Dreamweaver makes it easy for you to build pages with CSS layouts
by providing 16 pre-designed layouts that work across different browsers.
Using the pre-designed CSS layouts that come with Dreamweaver is the easiest way to create a page with a CSS layout,
but you can also create CSS layouts using Dreamweaver absolutely-positioned elements (AP elements). An AP element
in Dreamweaver is an HTML page element—specifically, a div tag, or any other tag—that has an absolute position
assigned to it. The limitation of Dreamweaver AP elements, however, is that since they are absolutely positioned, their
positions never adjust on the page according to the size of the browser window.
If you are an advanced user, you can also insert div tags manually and apply CSS positioning styles to them to create
page layouts.
About CSS page layout structure
Before proceeding with this section, you should be familiar with basic CSS concepts.
The basic building block of the CSS layout is the div tag—an HTML tag that in most cases acts as a container for text,
images, and other page elements. The following example shows an HTML page that contains three separate div tags:
one large “container” tag, and two other tags—a sidebar tag, and a main content tag—within the container tag.