I'm sorry, since I'm not familiar with using the Dreamweaver to develop the ASP.NET application so I cannot tell you how easy to use the Dreamweaver MX to fix the error. However, from the error description what I can say is that the web page that currently causes the error is using the Register directive for the code defined in the assembly which is specified in the Assembly and Namespace attributes of the directive. And the ASP.NET has no idea about the location of this assembly, so it cannot load the assembly, and as a result it is causing the error. To fix the error, IMO you need to tell the ASP.NET how to load your assembly either putting it in the bin folder or using the Web.config file if this assembly is deployed to the Global Access Cache (GAC). You may find a good response from their support site: http://www.macromedia.com/cfusion/webforums/forum/index.cfm?forumid=12[^] http://www.macromedia.com/devnet/dotnet/[^]