Change layout on Twenty Eleven Theme

I tried this code but it don’t work

#primary {
	float: left;
	margin: 0 -6.4% 0 0;
	width: 100%;
}
#content {
	margin: 0 34% 0 2.6%;
	width: 78.4%;
}
#secondary {
	float: right;
	margin-right: 2.6%;
	width: 18.8%;

My site : http://shop.vinhxomdoi.esy.es/