Since the CSS3 specifications are relatively new, not all browsers handle them the same way.

Eventually the vendor prefixes will be dropped and all browsers will support the standard version of the CSS code.

The most common browser prefixes are:

-moz = Mozilla browsers (Firefox) - uses the gecko layout engine
-webkit = Google Chrome, Apple Safari - uses webkit layout engine
-ms = Internet Explorer (MicroSoft)
-o = Opera

Transforms are handled differently by IE, Safari and Chrome, so to make them work you must write the standard code followed by browser-specific code:

div
{
transform:rotate(7deg); /* future web standard */
-ms-transform:rotate(7deg); /* IE 9 */
-webkit-transform:rotate(7deg); /* Safari and Chrome */
}