IE9 will support opacity

On August 18, Ted Johnson (Microsoft Program Manager Lead for Web Graphics) announced on the IE blog that IE9 would support the CSS3 Color module , and in particular, support the opacity property instead of Microsoft's own alpha filter . However, support for the alpha filter will remain in compatibility modes (Quirks, IE7, and IE8), for which, on the contrary, opacity is not planned.

Thus, in order for CSS to work in all versions of the Microsoft Explorer, it is enough to describe transparency with two properties in a row:

. Some Class {
    opacity: 0.3;
    filter: alpha (opacity = 30);
}

If you set the transparency not with CSS, but with a javascript, then make sure that the script does not assume that all versions of IE understand filter and do not understand opacity : such an assumption will be incorrect with respect to IE9. Instead, Ted Johnson recommended using the opacity property in scripts depending on the value of some (pre-computed) variable that determines browser support for this property:

var useOpacity = (typeof document.createElement ("div"). style.opacity! = 'undefined');

For more detailed examples, you can refer to his blog post.