JQUERY how to get clicked tr or td table's ID ??

Use the below line of code .

$(this).closest('table').attr('id');

JQUERY TO COUNT TOTAL SELECTED CHECKBOXES

function checkTotalSeleted(){

   var lengthTotal = $('input[name=ids]:checked').length;

    if(lengthTotal!="0"){
$("#totalSelected").html("Total selected: +lengthTotal);

    }else{
    $("#totalSelected").html("");
   }
}

AJAX call using JQuery

AJAX call using  JQuery 

Example
$.ajax({url:validateUrl,
type: 'POST',
async:false,
data: 'method=validateCondition&condition='+data,
success: function(answerFromServer){
onSuccessValidateCondition(answerFromServer,fieldId);
}
});

Description:
url: URL where the AJAX call will be send.
type: POST , GET etc
async: true/false (Default is True, True will allow other content of the page to load independently of the ajax call. false is reverse of it) 
data: the particular method of the servlet you want to call, and other parameters you can append.
sucess: function(answerFromServer){} : answerFromServer will contains the data sent by server in response of the ajax call