Pages getting cut off

Many of the pages on my site seem to be getting cut off (the problem is even worse in I.E. than Firefox, for some reason).

Here’s an example on my contact page – you’ll notice the “submit” button is only half visible: http://plaidcupcake.com/contact-me/

I’ve tried adding a bottom margin to both #content and #container and neither worked. I’m a newbie at all of this, so any help is appreciated!