var idno = 2;
        var strId = "new_element" + idno.toString;
        function addNewElement() {
            var mainDiv = document.getElementById('more_element_area');
            var innerDiv = document.createElement('div');
            innerDiv.setAttribute('id', 'divId' + idno);
            var generatedContent = '<p name="new_element' + idno + '" id="new_element' + idno + '" onkeyup="valid("new_element" + idno);" contentEditable="true" class="pAdd">This is my text box' + idno + '</p>';
            innerDiv.innerHTML = generatedContent;
            mainDiv.appendChild(innerDiv);
            idno++;
        }
        function valid(idx) {
            var el = document.getElementById(idx);
            var val = el.innerHTML;
            var re = /^[^\s()<>@,;:\/]+@\w[\w\.-]+\.[a-z]{2,}$/i;
            if (re.test(val)) {
                document.getElementById(idx).contentEditable = "false";
            }
        }

<div id="more_element_area">
        <div>
            <%--<input type="text" name="new_element1" value="This is my text box 1" />--%>
            <p name="new_element1" id="new_element1" contenteditable="true" onkeyup="valid('new_element1');">
                This is my text box 1</p>
        </div>
    </div>
    <a href="javascript:void(0)" onclick="return addNewElement()">+ Add more text box</a>