On the other hand, the Mozilla and Safari (-moz-opacity and ??“khtml-opacity)
properties do follow the rules, and although the code won??™t validate, you can be
sure these properties will be relatively safe from conflicts.
Even though browsers such as Firefox, Opera, and Safari eventually implemented
the CSS3 opacity property, the style rules like the one in the example above still
continued to work, ensuring a seamless transition between the old and the new.
As you can see, extensions can be useful, and can provide a measure of longevity;
however, it??™s not advisable to rely on the availability of extensions. It??™s also possible
that CSS3 properties may be changed before they become the standard. Therefore,
as the W3C states, ???Authors should avoid vendor-specific extensions.???
Due to the very nature of vendor-specific extensions, they??™re not well documented
for public use, so it??™s difficult to provide full and accurate listings of all the available
extensions. The following links may be used as a guide, but we urge you to carry
out your own research if you want to use these extensions:
?– Internet Explorer CSS Attributes: Index6
?– CSS Reference: Mozilla Extensions7
?– CSS3 Columns in Mozilla8
6 http://msdn.
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