Sticky footer: why could overflow:auto; and position:relative; be needed?

[sweetie21]

I'm using css sticky footer from http://www.cssstickyfooter.com/style.cssWhy do we need: \[code\]#main{overflow:auto;}\[/code\] and \[code\]#footer{position: relative;}\[/code\]?Seems like it works without it (I'm not talking about Opera and IE fixes).