For Cross-Browser Compatibility :
Example Goes Below :
<html><body class="entire-webpage"></body></html>
.entire-webpage{
zoom: 2;
-moz-transform: scale(2);/* Firefox Property */
-moz-transform-origin: 0 0;
-o-transform: scale(2);/* Opera Property */
-o-transform-origin: 0 0;
-webkit-transform: scale(2);/* Safari Property */
-webkit-transform-origin: 0 0;
transform: scale(2); /* Standard Property */
transform-origin: 0 0; /* Standard Property */
}