Simplest thing I've found for responsive sites, works pretty well

responsive.css

/* REMEMBER TO CHANGE THE FONT SIZES FOR YOUR OWN WEBSITE */

/* higher than 900px wide screen */
body {
	max-width: 700px;
	padding: 0 10px;
	margin: 0 auto;
}

/* 900px or smaller width screen */
@media (max-width: 900px) {
	html {
		font-size: 20px;
	}
	body {
		max-width: 600px;
		padding: 0 10px;
		margin: 0 auto;
	}
}

/* 400px or smaller width screen */
@media (max-width: 400px) {
	html {
		font-size: 16px;
	}
	body {
		max-width: 300px;
		padding: 0 10px;
		margin: 0 auto;
	}
}