In my current project I have quite complicated structure, more than 10 modules and each module has it’s own styles. To speed up compiling process I have splitted main project with modules and all styles to different projects in one workspace. On top of that in styles project bit-release folder is linked to html-template folder of the main project. So when I do Build release or Clean for styles project it automatically copies (merges) swf files to my main project.

Everything was working fine until recent time when I was needed to create programmatic skin and use it within CSS file.

.mainDataGrid
{
    backgroundAlpha : 0;
    borderSkin : ClassReference("mx.skins.ProgrammaticSkin");
    headerSortSeparatorSkin : ClassReference("mx.skins.ProgrammaticSkin");
    horizontalSeparatorSkin : ClassReference("sg.denisvolokh.skins.BrandedSeparator");
    verticalSeparatorSkin : ClassReference("sg.denisvolokh.skins.BrandedSeparator");
}

It is simple task and there is technique for it but Flash Build 4 compiler does not allow to do it with nested CSS. It is known bug http://bugs.adobe.com/jira/browse/FB-11925, moreover this bug was open in 2008 and still open and as I see from comments and from some post on stackoverflow people are still fighting with it.

Here is my solution for this bug. If you put all your programmatic skin classes in a separate library project and link this library to you project with styles, it will work as It is supposed.