When you develop a web application it may be a chance you can get below error:
WebForms UnobtrusiveValidationMode requires a ScriptResourceMapping for 'jquery'. Please add a ScriptResourceMapping named jquery(case-sensitive).
To overcome above error make sure you have below entry in your web.config file:

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