Ninja CSS Blog

filter:alpha(opacity=90);
-khtml-opacity: 0.9;
-moz-opacity:0.9;
opacity: 0.9;

Now for the different ways of setting opacity…

For Internet Explorer:

filter: alpha(opacity=90);

For Mozilla:

-moz-opacity: 0.9;

For Safari (current):

opacity: 0.9;

This is the important one. It is the current standard supported by Safari, Opera and Firefox

For Safari (old):

-khtml-opacity: 0.9;

This is for older versions of Safari, back before it adopted webkit (which is what you use for something like round borders).

.someClass {
  padding-top: 10px; /* shows in all browsers */
  *padding-top: 10px; /* shows in IE7 and below */
  _padding-top: 10px; /* shows in IE6 and below */
  *padding-top: 10px;_padding-top:10px; /*shows in IE7 and IE6 */