The only three generic families that are safe for generic cross-compatible development are serif, sans-serif, and monospace.
The cursive family is by default mapped to MS Comic Sans in MSIE. Sadly, Comic Sans is nowhere near cursive. Not to mention that in CSS, 'cursive' means 'any font that appears hand-written'.
The fantasy family is simply any font that doesn't fit into any other categories. This generally means wild variation between platforms.
Unfortunately, Netscape 4 ignores the cursive and fantasy families altogether. Go ahead and set all of the specific fonts you want, but leave the generic fonts to serif, sans-serif, and monospace.
Wilson, Brian. "Font-Family" Cascading Style Sheets Properties 1996-2002. http://www.blooberry.com/indexdot/css/properties/font/fontfamily.htm August 17, 2002.