The following “yellow screen” error occurs in your application:
A potentially dangerous Request.Form value was detected from the client
Microsoft .NET Framework causes this due to enhanced security features (request validation). Request Validation has detected a potentially dangerous client input value, and processing of the request has been aborted. This value may indicate an attempt to compromise the security of your application, such as a cross-site scripting attack. You can disable request validation by setting validateRequest="false" in the Page directive or in the configuration section of Web.config. Note that if you are using .NET 4.0 or higher, you will also need to set requestValidationMode="2.0". However, it is strongly recommended that your application explicitly check all inputs if you use these settings.
Step 1: Locate the ASP.NET settings in:
<Application Folder>\Web.config
Step 2: Set the value of validateRequest attribute of pages element to false.
<pages validateRequest="false" />
Step 3: (Only for .NET 4.0 and higher) Add the requestValidationMode attribute with the value of 2.0 to the httpRuntime element.
<httpRuntime maxRequestLength="10240" requestValidationMode="2.0" />
Additional information on this topic can be found at:
http://support.esri.com/index.cfm?fa=knowledgebase.techarticles.articleShow&d=26147
Part VII: Troubleshooting Applications
Application Runs But No Data is Displayed