Jquery not working in asp.net

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jQuery

Sir, Please guide me . This is properly working on normal page but not working while change style of div display : block to None.

$(function () {
           // debugger;
            $('#ctl00_ContentPlaceHolder1_lnk_vol_instruction').hover(function (event) {
                //var toolTipcontents = $(this).attr('title'); //ToolTip
                var toolTipcontents = $('#ctl00_ContentPlaceHolder1_txtInstructions').attr('value'); //ToolTip
                $('<div class="tooltip"></div>').text(toolTipcontents)
            .appendTo('#ctl00_ContentPlaceHolder1_lnk_vol_instruction')
            .css('top', (event.pageY - 40) + 'px')
            .css('left', (event.pageX - 60) + 'px')
            .fadeIn(4000);
            }, function () {
                $('.tooltip').remove();

            }).mousemove(function (event) {
                $('.tooltip')
        .css('top', (event.pageY - 40) + 'px')
        .css('left', (event.pageX - 60) + 'px');
            });

        });