when we create [WebMethod] in web serivces then it should be static or non static what is the concept?

This is the example of Code Project.
Static ?????

using System;
using System.Collections.Generic;
using System.Linq;
using System.Web;
using System.Web.Services;

[WebService(Namespace= "http://tempuri.org/")]
[WebServiceBinding(ConformsTo= WsiProfiles.BasicProfile1_1)]
// To allow this Web Service to be called from script, using ASP.NET AJAX, uncomment the following line.
//
[System.Web.Script.Services.ScriptService]
public class Service : System.Web.Services.WebService
{
public Service ()
{

//Uncomment the following line if using designed components
//InitializeComponent();
}

[WebMethod]
public int Area(int l, int b)
{
return l * b;
}

[WebMethod]
public int Perimeter(int l, int b)
{
return 2 * (l +b);
}
}