/* Large Devices, Wide Screens */
@media only screen and (min-width : 1200px) {
 #chart_div{width: 900px; height: 500px;	}
}
/* Extra Small Devices, Phones */ 
@media only screen and (max-width : 480px) {

    #chart_div{width: 400px; height: 240px}

}

/* Custom, iPhone Retina */ 
@media only screen and (max-width : 320px) {
     #chart_div{width: 300px; height: 160px}
}