Another bit of CSS that I use in CSlide that didn’t work in IE7 is opacity – http://www.w3.org/TR/2011/REC-css3-color-20110607/#transparency.
After digging around various forums, I found that the solution is to add a filter property (which is not part of the CSS standards and is only supported by IE), as well as the opacity, as follows:
filter: Alpha(Opacity=80); /* IE */ opacity: 0.8; /* Standards-compliant browsers */