I have a great problem with Web.Config, I need to see error of my page and resolve it in asp.net web form and web config, but when Error Occurred, I see another error and I see this:
customErrors mode to Off or On Or RemoteOnly,
When you're having issues with configuration, make sure that your settings isn't overridden.
In this case, your server might have a configuration
<deployment retail="true" /> that overrides application settings and disables trace output, custom errors, and debug capabilities.
Change the value to "false"
<deployment retail="false" />