handle Error 500 - Internal server error through Webconfig

Dear All,
I wanted to handle the error "500 - Internal server error." through the web config like i am handeling "404", i put the following but its not handelling!!

<customErrors mode="On" defaultRedirect="~/Portals/Error" redirectMode="ResponseRedirect"> <error statusCode="403" redirect="~/Portals/Error" /> <error statusCode="404" redirect="~/Portals/Error" /> <error statusCode="500" redirect="500.cshtml" /> <error statusCode="503" redirect="ErrorPage503.aspx" /> </customErrors>
<system.webServer> <httpErrors> <remove statusCode="404" subStatusCode="-1" /> <remove statusCode="500" subStatusCode="-1" /> <error statusCode="404" prefixLanguageFilePath="" ...