Does the WEB EDITION of Windows Server 2003 limit the number of simultaneous incoming requests for an ASP .NET 2.0 website running under IIS 6? In testing, HTTP requests seem to start to get queued up at the twelve concurrent request. I can find plenty of other Web Edition limitations listed in Microsoft documentation, but nothing regarding a limit on incoming HTTP requests. Is there a limit?

No, there should not be a limit.

But, if you're running MSDE, <that> has a concurrent connection limit which would cause a domino effect.

If that is your issue, it's caused by poor programming practice following "traditional" recommendations leaving database connections open. MS for years has generally recommended that you forcibly close your database connections with every query result to achieve scalability.