set default text in dropdownlist

bind city like

ddlCity.DataSource = CityDataSet;
                   ddlCity.DataValueField = "CityID";
                   ddlCity.DataTextField = "CityName";
                   ddlCity.DataBind();
                   ddlCity.Items.Insert(0, "Please Select City");

Thanks i did it

NOw how i can do it for TextBox i want write some text in TextBox and when user click on Textbox that text willdelete and user type new text on it 

refer:

http://www.aspsnippets.com/Articles/Watermark-TextBox-using-JavaScript.aspx

thanks alot