Description: 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. However, it is strongly recommended that your application explicitly check all inputs in this case.

Exception Details: System.Web.HttpRequestValidationException: A potentially dangerous Request.Form value was detected from the client (txbFrom="...m Taylor <postmaster@smartma....")

Source Error:
An unhandled exception was generated during the execution of the current web request. Information regarding the origin and location of the exception can be identified using the exception stack trace below.

Stack Trace:
[HttpRequestValidationException (0x80004005): A potentially dangerous Request.Form value was detected from the client (txbFrom="...m Taylor <postmaster@smartma....").]

   System.Web.HttpRequest.ValidateString(String s, String valueName, String collectionName) +230
   System.Web.HttpRequest.ValidateNameValueCollection(NameValueCollection nvc, String collectionName) +99
   System.Web.HttpRequest.get_Form() +121
   System.Web.UI.Page.GetCollectionBasedOnMethod() +70
   System.Web.UI.Page.DeterminePostBackMode() +47
   System.Web.UI.Page.ProcessRequestMain() +2106
   System.Web.UI.Page.ProcessRequest() +218
   System.Web.UI.Page.ProcessRequest(HttpContext context) +18
   System.Web.CallHandlerExecutionStep.System.Web.HttpApplication+IExecutionStep.Execute() +179
   System.Web.HttpApplication.ExecuteStep(IExecutionStep step, Boolean& completedSynchronously) +87

SOLUTION
1. Explore to the directory that WebAdmin is installed.
2. Open web.config in NotePad.
3. Add the line: <pages validateRequest="false" /> inside the <system.web> section as shown below.

   <system.web>
    <pages validateRequest="false" />
    <compilation defaultLanguage="c#" debug="false" />
    <customErrors mode="RemoteOnly" />
    <authentication mode="Windows" />
    <trace enabled="false" requestLimit="10" pageOutput="false" traceMode="SortByTime"    localOnly="true" />
    <sessionState mode="InProc" stateConnectionString="tcpip=127.0.0.1:42424" sqlConnectionString="data source=127.0.0.1;user id=sa;password=" cookieless="false" timeout="20" />
    <globalization requestEncoding="utf-8" responseEncoding="utf-8" />
  </system.web>

4. Save the file and exit.
5. Try to access WebAdmin again.