In the old days we always created text only versions of sites so that users with old software could use it without the graphics crashing their browser. Then as releases of HTML advanced, we had to worry about features from version 4 working with version 1. Round and round the mulberry bush the browser chased the user. Whenever you build a page, it is critical you check it with both of the big boys, Netscape and Internet Explorer. You also need to decide which versions of those browsers you are going to support, but more of that in a moment.
Computer users have loyalty to hardware and software.
Hey, I'm an old Mac user who only converted to DOS when Microsoft failed to release Office 97 on that platform. This loyalty is primarily a comfort issue, but not that different from Chevy fans referring to Ford's as Fix Or Repair Daily. I still have friends who use PINE for their email, and even one who refuses to give up his DOS 3.1 box because it does all he needs. If you pay any attention to the world, you realize that Netscape is toast. Pretty soon Bill will own my bank too.