You can use css3 transform:
-webkit-transform: scale(0.5); /* Chrome, Safari 3.1+ */
-moz-transform: scale(0.5); /* Firefox 3.5-15 */
-ms-transform: scale(0.5); /* IE 9 */
-o-transform: scale(0.5); /* Opera 10.50-12.00 */
transform: scale(0.5);
Calculate the scale ratio and apply the rules with this ratio in your script.
Do not forget to set left and top property of the transformized element as the offset ratio of the full width and height:
offsetRatio = (ratio - 1) / 2;