I've seen multi-word font families encapsulated with single quotes, double quotes and no quotes.

Are there browser compatibility issues with any of the above?

Example:

No Quotes:
font-family:Lucida Sans Unicode, Lucida Grande, sans-serif;

Single Quotes:
font-family:'Lucida Sans Unicode', Lucida Grande', sans-serif;

Double Quotes:
font-family:"Lucida Sans Unicode", "Lucida Grande", sans-serif;

Mixed:
font-family:"Lucida Sans Unicode", Lucida Grande, sans-serif;