//txtEmail.Attributes["onFocus"] = string.Format("js_waterMark_Focus('{0}', '請填寫正確個人電子郵件','WaterMarkedTextBox', 'NormalTextBox')", txtEmail.ClientID);
//txtEmail.Attributes["onBlur"] = string.Format("js_waterMark_Blur('{0}', '請填寫正確個人電子郵件','WaterMarkedTextBox', 'NormalTextBox')", txtEmail.UniqueID);

function js_waterMark_Focus(objname, waterMarkText, waterMarkStyle, normalStyle)
{
    obj = document.getElementById(objname);
    if(obj.value == waterMarkText)
    {
      obj.value="";
      obj.className = normalStyle
    }
}
function js_waterMark_Blur(objname, waterMarkText, waterMarkStyle, normalStyle)
{
    obj = document.getElementById(objname);
    if(obj.value == "")
    {
        obj.value=waterMarkText;
        obj.className = waterMarkStyle
    }
    else
    {
        obj.className = normalStyle
    }
}