For a long time, IE's alternative to the CSS opacity property has been the filter property:
filter: alpha(opacity=50);
If you Google "IE8 opacity", you'll find a number of pages (including one at quirksmode.org) telling you that Microsoft removed support for opacity in a preview release of IE8, and then put it back in, but with a new syntax. These pages assert that in order to achieve the same half-transparent effect as above, you must write (note the -ms- prefix and the quoted value):
-ms-filter:"progid:DXImageTransform.Microsoft.Alpha(Opacity=50)";
As far as I can tell, however, all of these pages are based on preview releases. My (very simple) testing indicates that the old syntax continues to work in IE8, and there is no need to add a second non-standard property to our stylesheets for IE8.
This post at the IE blog backs me up on this (scroll down to the section titled "A Pragmatic Solution") Or at least I think it backs me up. The post tries to explain and justify the initial change to the filter syntax but it just doesn't make much sense.
Someone please correct me if I'm wrong. Are there versions of IE8 in the wild that don't support the old filter syntax?
@__DavidFlanagan
