A client calls you one day. He says he cannot access your web site. So you hurry up to check what's wrong. Everything seems perfectly normal. The problem is that the client is using Internet Explorer 5. Kaboom! So what's next? Internet Explorer 5 has an infamous and poor support to web standards, so even the most simple things get complicated in this browser, not to say impossible to do. The most obvious thing to do is to convince your client to upgrade his browser. Here another problem: he should upgrade his operating system as well. Is there a solution?
Yes. Do you remember Netscape 4? Most developers simply provided a basic pages to this browser without all the CSS and JavaScript enhancements. Same thing applies to Internet Explorer 5. Further, developers were used to insert an upgrade message for Netscape 4 users to make these users upgrade their obsolete browser. Same thing here. Besides this solution, there's nothing, really nothing you can do to make a Web 2.0 application or web site fully work in Internet Explorer 5.
By the way, the call was real, not just an example. sad