Invalid Embed directive in stylesheet - can't resolve source 'Embed(source = "my_resource.swf", symbol = "my_skin")'

If you are getting just one or two errors in your css, check the path of those resources.

Are you getting hundreds of such errors in your css, for all the resources? Then your css might be good ;-) Just comment out the css file in your source and take a look, you might have some broken embed resource path in your code (mxml or as). Fix it, you will be good.