Canvas Height options "Auto-resize" vs "Fluid" in App Settings

A question about Canvas Height setting in the 开发者_JAVA技巧Facebook Settings.

There are 2 options Auto-Resize and Fluid and they seem to function in the same way.

In the Canvas Tutorial, it seems that the 2nd option should be scroll bars for Canvas Height, so I'm assuming that Fluid option is a new feature.

But what is the difference between Canvas Height set to Auto-Resize or Fluid?

Here is the documentation

http://developers.facebook.com/blog/post/549/

If you would have placed your cursor over the question sign near the Canvas Height option, you might have seen this:

"Settable allows you to set the height via FB.Canvas.setSize() method in JavaScript SDK with default set to 800px. Fluid sets the height dynamically to fit the page and shows scrollbars if content exceeds the page size."

Also, the options are not Auto-Resize and Fluid, but Settable and Fluid