The "voice-family" hack, better known as the Tantek Celik Box Model Hack, is used to hide specific CSS rules from IE4/5 on Windows because of incorrect implementations of the CSS standard in those browsers. It is an attempt to deliver the most correct single stylesheet to all browsers, without resorting to browser sniffing and multiple stylesheets.
Ironically this hack is the result of many man-hours (months?) of experimentation and testing to develop a standards-compliant stylesheet that works across older, newer, and future browsers. It is one of several workarounds that been created to make up for the horrible state of browser compliance to the CSS standard.
See Jeffrey Zeldman's Designing with Web Standards for an in-depth look at why adhering to standards (as much as possible) is a worthy goal, and why using browser sniffing and multiple stylesheets only causes headaches for the developer:
http://www.amazon.com/Designing-Web-Standards-Jeffrey-Zeldman/dp/0321385551/
One example is the arms race to keep up with browser/operating system combinations, not to mention mobile phones and other future devices with browsing capability. The detection code has to be changed with each new combination, and because of the way that many browsers masquerade as Netscape Navigator, detection can become a full time job.
Another good reference is the Web Standards Project, which has a lot of good information and tutorials on the subject:
http://www.webstandards.org/
If you move your coding style towards standards-compliance, you will generally not have to be as concerned about the release of future browsers. Yes, you still have to test against them, but you don't have to write and then test custom stylesheets for each one.