function add_field() 
    {
        var form = document.getElementsByTagName('form')[0],
        input = document.createElement('textarea');
        input.setAttribute('type', 'textarea');
        input.setAttribute('name', 'item');
        form.appendChild(input);

    };
    
var count = 0;

function contador() 
    {
        
        count++;

        if(count == 10){
            alert("QWERTY");
   document.getElementById('btn').disabled=true;

        }

    };
    <script src="https://ajax.googleapis.com/ajax/libs/jquery/3.2.1/jquery.min.js"></script> <!-- add Jquery CDN -->

    <link href src="https://maxcdn.bootstrapcdn.com/bootstrap/3.3.7/css/bootstrap.min.css" rel="stylesheet" media="screen">



    <script src="https://maxcdn.bootstrapcdn.com/bootstrap/3.3.7/js/bootstrap.min.js"></script> <!-- add Bootstrap CDN -->

    <link href="design.css" rel="stylesheet" medi="screen"> <!-- Add css in html -->


    <div class="container">
        <div class="row">
            <div class="col-lg-12 tabela">
                linha azul

            </div>
        </div>
    </div>