How do you set the background color for a variable height page?

[wein]

I have a web page that is minimum-height of 700px, but could be more. How do I use CSS to make sure that the body always has a background-color?\[code\]body { min-height: 700px; background: red;}\[/code\]will not work since the body height will only fill in up to 700px, and doesn't 'know' when the browser window is bigger.