I was working on a website the other day which had the usual CSS left, middle and right column, with the middle column being the viewport, or area where the most content was placed.  Anyway, the viewport had too much information on it, causing the content to spill over into the body (yes, I know the viewport is in the body, but I think you get the drift). 
Anyway, I remember setting the viewport before and found the following code in another project of mine, with comments to assist:
#container {
width: 1400px;
margin: 20px auto 0px auto; /* Just your normal margin */
text-align: left; /* Obvious */
background: white; /* Obvious */
border: solid 1px black; /* Obvious */
min-height: 100%; /* Causes the page to be as large as required. */
/* If little content, will be as large as the area INSIDE the browser window */
margin-bottom: -100px; /* Allows an area at the bottom of the screen to */
/* be used for a footer, if required*/
position: relative; /* Obvious */
}
Just to ram home the comment above, that x will allow you to place a footer CSS class in your code, showing such things as copyright info, company info or email info, at the bottom of your website, safe in the knowledge that no matter how much data you have in the viewport, the copyright information will always be at the bottom of the page, just after the content and floating somewhere else.
What are your thoughts on how to set the viewport so that it doesn't look too big?