lovely http header validator with an special focus on whether the responses are cacheable or not.

"Wingman validates pages directly from your browser. So, you don't need to submit your pages manually to an external site. ... Most validators are (by definition) pedantic. We've designed Wingman to be more human. When you encounter errors that you're prepared to live with you can choose to ignore them. And Wingman will remember."

"This page allows you to check what kind of layout mode is triggered when a page is served with a certain DOCTYPE and content type combination."