@media only screen and (min-width: 1200px) { ...some rules }
@media only screen and (min-width: 960px) and (max-width: 1199px) { ...some rules }
@media only screen and (min-width: 768px) and (max-width: 959px) { ...some rules }
@media only screen and (min-width: 481px) and (max-width: 767px) { ...some rules }
@media only screen and (max-width: 480px) { ...some rules }
aslo see
www.rockettheme.com/blog/team/1551-respo...ocketthemes-solution