User1622957740 posted
Integrated mode can dynamically re-route a request via a web.config option
<system.webServer>
<modules runAllManagedModulesForAllRequests="true">
which ensures that all requests are routed to ASP.NET including extensionless Urls used for typical routing apps.
Classic mode doesn't use that switch, so you need a wildcard script map.
There's more info here:
http://tugberkugurlu.com/archive/running-asp-net-mvc-under-iis-6-0-and-iis-7-0-classic-mode---solution-to-routing-problem
Even though that message talks about MVC the same applies for Web forms.
Now, all that said - why do you need to use classic mode? Especially if you're planning on using routing integrated mode is a much better and more efficient choice...
+++ Rick ---