WebForms UnobtrusiveValidationMode requires a ScriptResourceMapping for 'jquery'. Please add a ScriptResourceMapping named jquery(case-sensitive).

After adding the built in validating controls like required field validator in my case I added a new web form and then after adding the required field validator controller in the form the form got compiled but after running we can see the above error on the browser. The solution is that  we need to add  a new key into to the web.config file under the <appSettings> section

In Web.config

  <appSettings>

    <add key="ValidationSettings:UnobtrusiveValidationMode" value="None" />

  </appSettings>