Hello,
If you proper apply validation controls in your page.aspx e.g.
<asp:requiredfieldvalidator runat="server" id="rfv1" controltovalidate="txtName" errormessage="Required" forecolor="Red" xmlns:asp="#unknown" />
You just need to change your web.congig file and just add below code inside configuration tag.
<appSettings>
<add key="ValidationSettings:UnobtrusiveValidationMode" value="None" />
</appSettings>
That's all.