Some of IE CSS filters (gradients, for example) use #ARGB colors. The CSS packer tries to minify them assuming they are #RGB. So, for example, the following code:

filter:progid:DXImageTransform.Microsoft.gradient(startColorstr=#FF003300,endColorstr=#FFCC33CC);

Is minified into:

filter:progid:DXImageTransform.Microsoft.gradient(startColorstr=#F0300,endColorstr=#FC3CC);

Steps to reproduce

1. Paste the first code in a CSS block
2. Enable packer (DevelopmentMode=disabled)
3. View generated stylesheet