It is not possible to use every CSS command in a FeedWind custom CSS. For example, -repeat commands for wrapper images in the header are not supported. There are simply too many CSS operators and parameter combinations beyond what is necessary for controlling a feed’s appearance; thus, the simplest way to test if your custom CSS works with FeedWind is to try different configurations, refresh the web page, and observe how it appears. In that sense, custom FeedWind with CSS is no different than using to design a website, in that some trial and error is required.
The table below should give an acceptable overview on how your CSS should be structured, and the example file that follows is for you to see these parameters in action with a file that can be uploaded to your own feed and used as a template to tweak.