Under the new ASP.NET validation framework, how do the validation controls determine when to use client script vs. server-side code? For example, regular expression support is weak or non-existent in browsers like IE and Netscape 3. Would ASP.NET default to server side in those cases? Is this a configurable setting? What is the performance hit (to the server) and the between page delay time when the API now includes this type of "dynamic" per page validation?

Our client side validation requires both EcmaScript (JScript) 1.2 and the MSDOM. In Beta1, if the UserAgent is IE4 or better, and the page's ClientTarget is Auto (the default) we'll render client script. Or, if ClientTarget is UpLevel, we'll render client script without regard for the UserAgent. We are looking at making this more flexible in Beta 2.