$('#bt1').click(function () {
if(document.getElementById("drop_down_button1").style.display=="none"){
$('#drop_down_button1').slideDown('slow');
}else{
//document.getElementById("drop_down_button1").style.display="none";
//// if i uncomment above line and comment blow one. then it works.
$('#drop_down_button1').slideUp('slow');
}
});