HTML and CSS Reference
In-Depth Information
up of only type selectors. But within each group the number of selec-
tors for each type is the significant factor.
One of the original uses for JavaScript when it was introduced by
Netscape back in 1995 was for rollover effects : changing a background
image when the mouse pointer enters or leaves an element. Rather than
require an entire scripting language for a simple visual effect like this,
the ability to select elements based on user activity has been built into
CSS with pseudo-classes.
This example is a page with a para-
graph element:
<p>Hover me</p>
By default, the paragraph is black
text on a white background.
The notation for a pseudo-class is a
colon followed by a keyword. For
rollover effects, the keyword is hover :
p:hover { background-color: #000; }
This rule sets the background of the
element to black when the mouse
pointer hovers over the element.
It's also possible to use pseudo classes with combinators,
defining rules for children of an element depending on its
dynamic state. Several interesting effects are possible only
when you do this. Let's look at a simple example.
Search WWH ::

Custom Search