"Vendor" prefixes as they are known are there so you can use some newer CSS rules in that browser until the browser version actually implements the real thing.
So for newer CSS rules it's always a good idea to use the default CSS rule and apply vendor prefixes as required. If the users browser version is old it may use the vendor prefixed style, or if it's more up to date it will use the normal rule.
Here's an example:
-moz-border-radius: 12px; // for older firefox browser versions
-webkit-border-radius: 12px; // for older webkit browser versions
border-radius: 12px; // normal/default used by new browsers
So if, say, Firefox drops -moz-border-radius at some point it will simply ignore that rule and use the default border-radius instead.