One of my facebook canvas applications always display the vertical and horizontal scrollbars with it, which is very annoying. By looking into the html source code with firebug, I found the app is hosted inside the <ifram> element with "smart_sizing_iframe" class. While another app without the scrollbars is hosted inside the <ifram> element with "canvas_iframe_util" class. I am pretty sure that my app code is the same in terms of canvas size setting.
After visiting my app settings from https://developers.facebook.com I got the tricky: go to the "canvas setting" under "On Facebook", you have two option for IFrame size: "Show Scrollbars" and "Auto-resize". By selecting "Auto-resize" and save, then refresh your application page, then you got it! Yes, the scrollbar get removed.
