How to identify if a webpage is being loaded inside an iframe or directly into the browser window?

Question

I am writing an iframe based facebook app. Now I want to use the same html page to render the normal website as well as the canvas page within facebook. I want to know if I

Answer 1

if (window.frames.length != parent.frames.length) { page loaded in iframe }

But only if number of iframes differs in your page and page who are loading you in iframe. Make no iframe in your page to have 100% guarantee of result of this code