marketing-site | Astral 's Marketing Site

I'm trying to use Foundation Building Blocks to make a web page. The issue that I've run into is that I can't get the UI building blocks in the Marketing Kit to render the way that I expect. That is, my page doesn't render the same as the sample building blocks do. For example, let me describe what I've encountered with the Marketing 3-up Feature Section (http://foundation.zurb.com/building-blocks/blocks/marketing-site-three-up.html)

It looks like the building block example that loads up in the iframe on that page doesn't use foundation.css but instead uses an app.css that includes far more stuff in the selectors than foundation.css does. (http://foundation.zurb.com/building-blocks/blocks/marketing-site-three-up-iframe.html) If my own page uses foundation.css, I don't get an expected rendering result. But if it instead uses the app.css page in that example page, it works. But that app.css doesn't appear to be documented in the instructions for using the Marketing Kit.

What am I missing?