If your web.cofig file doesnt run (Even though the error keeps telling you to modify the web.config to show the errors) this is 99% of the time due to ASP.NET failing before it completes or even starts the web.config file. This means that you either have a serious error before the web.config file. It is also possible that you might be trying to run asp.net version 2 when your site is setup for asp.net version 1.1 or vise versa. You can check your version of asp.net in the control pane, check previous knowledgebase article for changing asp.net versions. If your application will not run you may need to get support to check this for you.