HTML and CSS Reference
Figure 9-3. Centralizing with negative margins
The corresponding CSS ruleset can be written as shown in Listing 9-2.
Listing 9-2. Centralizing with Negative Margins
Flexible Layouts with Responsive Web Design
The first attempt to allow access to content and basic functionality of a web site and provide an advanced version of
the same site to browsers with better or more complete web standards support is known as Progressive Enhancement,
which was introduced in 2003. The corresponding approach is often referred to as Graceful Degradation . By applying
best practices such as creating a correct document structure in the markup, web designers can contribute not only to
Progressive Enhancement, but also accessibility and overall code quality.