Every browser has different CSS properties for less-used actions like: transparency or opacity.
It was something weird to do transparency on your web page because there are lot of different web browsers. To make that easy, I have collected information and generated a CSS class that will work on most of the browsers.
See the Code below:
filter:alpha(opacity=75); is used for Internet Explorer.
-moz-opacity:0.75; is used for Mozilla, Firefox, Netscape browsers (old versions).
-khtml-opacity: 0.75; is used for old versions of Safari.
opacity: 0.75; is used as a standard CSS property for browsers like Firefox 2+ and Safari 3+ and Opera