<script src="jquery.js"></script>
    <script type="text/javascript">
        var a = "aaaa";
        $(function () {
          
            $.ajax({
                type: "POST",  
                contentType: "application/json", 
                url: "Default.aspx/Time", 
                data: '{"abc":"' + a + '"}',
                dataType: 'json',
                success: function (result) {    
                    alert(result.d);
                }
            });
        });
    </script>

     [WebMethod] 
    public static string Time(string abc)
    {
        
        return abc;
       
    }

        var a = "aaaa";
        var b = "bbbb";
        $(function () {
          
            $.ajax({
                type: "POST",  
                contentType: "application/json", 
                url: "Default.aspx/Time", 
                data: "{a1:'" + a+ "',a2:'" + b + "'}",
              
                dataType:'json',
                success: function (result) {    
                    alert(result.d);
                }
            });
        });

   [WebMethod] 
    public static string Time(string a1,string a2)
    {
        
        return a1+a2;
       
    }