In updating my DHTML skills, I am learning how to implement a cross-browser document object model. The book I am using, though, was written a couple of years ago. the author shows how to sniff out a Netscape 4x, IE 4x, older, or newer browsers. The problem is that the author has assumed based on statements made at the time ofpublishing that the new 5x browsers are going to implement the same DOM standards. Is this true? Or should I also be checking on the new 5x and 6x version browsers?

Thanks