Originally Posted by mark87
Fwiw, in most cases, if not all, using CSS opacity renders the entire element semi-opaque. This means that any text, images, etc… will also be rendered semi-opaque.
In case that's not what the op is after…
If the idea is purely to have a semi-opaque/semi-transparent background, then you'll need to use a PNG24 image.
IE/Win doesn't natively support PNG24 semi-transparency, so you'll need to implement a proprietory CSS filter to kick-start the transparency in the PNG24 image.
IE5/Mac has buggy support for tiling of PNG24 background images, but it's a simple matter to use the band-pass filter
to supply IE5/Mac with overriding CSS that uses a single, larger, non-tiling background image which fills the background of the element.
I'm not sure of the IE/Win filter method's support for tiling background PNG24 images, but if it's a problem, you can use the larger, non-tiling background image in the IE/Win CSS override filter as well.