I host a Google App Engine (GAE) site under two domain names because the content is common but filtered to each domain.

I want to apply different branding depending on which domain name is used to arrive at the site. Let's inject different CSS depending on the value of Window.Location.getHostName(). At the end, you'll see a different site in your dev environment depending on whether you use http://127.0.0.1:8888/SkinIt.html?gwt.codesvr=127.0.0.1:9997 or http://localhost:8888/SkinIt.html?gwt.codesvr=127.0.0.1:9997 to access it from your browser.