HTML and CSS Reference
In-Depth Information
RGBA or HSLA isn't just about making things look cool; it can also improve
your web site's e
!
ciency. You don't have to take time to make alpha-
transparent PNGs to use as backgrounds, since you can just use a color in
the CSS, and the user agent doesn't have to download those images when
loading the site.
Styling Backgrounds and Borders
Aids in: progressive enhancement, e
"
ciency
CSS3 o
"
ers a whole host of new ways to style backgrounds and borders,
often without having to use images or add extra
div
s. Most of these new
techniques already have good browser support, and since they're mainly
used for purely cosmetic changes, they're a good way to get some
progressive enhancement goodness going in your sites right away.
Here are some of the new things CSS3 lets you do with backgrounds:
•
Multiple backgrounds on a single element:
You can now add more
than one background image to an element by listing each image,
separated by commas, in the
background-image
property. No more
nesting extra
div
s just to have more elements to attach background
images onto!
•
More control over where backgrounds are placed:
The new
background-clip
and
background-origin
properties let you
control if backgrounds are displayed under borders, padding, or just
content, as well as where the origin point for
background-position
should be.
