function book(url,title){
  if ((navigator.appName == "Microsoft Internet Explorer") && (parseInt(navigator.appVersion) >= 4)) {
  window.external.AddFavorite(url,title);
  } else if (navigator.appName == "Netscape") {alert("Due to a bug in Firefox, bookmarking this page will result in a bookmark that opens in the bookmarks sidebar rather than the main window. To correct this, after having added the bookmark, right-click on the new bookmark, select 'properties' and uncheck the box that says 'Load this bookmark in the sidebar'.")
    window.sidebar.addPanel(title,url,"");  
  } else {
    alert("This function is not implemented for your browser");
  }
}