iframe busters are intended to break a webpage out of an iframe inside another page so that they become the top level page

e.g. if I had an iframe in this answer with your site inside it, the role of an iframe buster on your site would be to bust your site out of my iframe and prevent me from using iframes to show your website

This is similar to frame busters, where a website may be encased in a frameset with a second frame up top showing a digg bar or advertisement. In this case, a frame buster would force the browser to display the website and only the website as intended by the author, rather than in a frame with potential advertisement or malware bundled in another frame.

In the provided example, the JavaScript is used to insert a script tag to a second JavaScript file which performs the actual frame busting. The JavaScript used in the html file linked simply obfuscates this process while loading different urls for different advertisements, each with different iframe html to insert.

The lengths gone to are likely to be a factor of a cat and mouse chase, as is common with frame busting techniques, where sites have written scripts to bust out of frames, and the companies responsible for framing the sites have written anti-frame busting scripts, so anti-anti-frame busting scripts have been written.

This is done for "take over ads". We use iframes (ADI - iframe vs ADJ - javascript) for a few reasons:

1 - they slow down the loading of your page content. 2 - they can break javascript on your page causing your page to stop functioning properly. 3 - worse case: they inject malicious code.

Using the iframe (ADI) approach the ads are isolated into their own document and can t interfere with the main web page.

However, there are cases when your marketing team wants to run take over ads. They are ads that expand outside their iframe window. For these ads the "iframe busting" approach was setup by most of the top advertising vendors. This approach requires you to host a file on your side that the ads can interact with and by pass the cross-domain restrictions of browsers.

Here is a comprehensive list of these files: http://www.adopstools.com/?section=miscellaneous&page=iframes

Iframe Busters are used to help certain type of rich media creatives perform their full function. FOr example an Expandable rich media will not expand if served into an Iframe without being able to bust out of the Iframe.

This is where the Iframe Buster comes into play.

The purpose of the Iframe buster is to allow the creative to break out of the Publishers Iframes so the creative can be fully functional.

Typically it s a file which needs to be placed in a folder on the sites domain.

So www.yoursitename.com/folder/iframebuster.html

This location will need to be referenced whenever you serve an Expandable ad into the Iframe.

What the iFrame Buster does is it allows an expandable banner to come outside of it s Ad Unit dimension. For rg. if you have a 300x250 ad slots and you have an 300x250 ad banner that expands to 300x500 on mouse over or on click then iFrame buster allows it break that 300x250 boundaries and give room to the banner to expand by 300x500.

Doubleclick iFrame buster us generally required if you have a Rich Media Creative like a Pushdown, PubBar or Expandable being hosted and served/setup in DART Studio.

Atlas has their own iframe buster code, MediaMind has addineyev2.html and similarly FlashTalking and other have theirs which are required to be hosted on the server where the ads are going to run.