opacity style

In style sheet, opacity effect is still in css3 draft now. Most of modern browser are supported opacity now, but they are very different.

Let say
.op {-moz-opacity:0.5; filter:(alpha:50);opacity:0.5}

Firefox's -moz-opacity has best support.
IE's filter only works for TD tag, not DIV tag.
Safari's opacity works for DIV, SPAN tag, but not TD tag.

Please note the difference between IE and Safari. They are totally opposite.