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Browser Bookmark Bingo

With the heated browser wars between Netscape’s Navigator and Microsoft’s Internet Explorer, you may find yourself switching from one to another to try out glitzy new features.

But switching browsers requires more than just downloading multi-megabyte files, running installers, and learning how to use the new features. If you are like me, you have dozens, even hundreds of bookmarks (called Favorites if you use Internet Explorer) that you want to keep using with your new browser with no hassles. Unfortunately, it is still unnecessarily difficult to move bookmarks from one browser to another, especially across platforms.

To get some insight into why browsers may not like each other’s bookmarks, let’s take a close look at how bookmarks are stored in Internet Explorer and Netscape Navigator.

(For ease of use, we’re going to call Netscape’s browser Navigator, though it can be part of the Communicator suite. Also note that this article was written while using version 3 of Internet Explorer and Navigator on the Macintosh, and version 4 of both browsers under Windows 95.)

Bookmark Formats — The Windows version of Internet Explorer stores bookmarks as separate files (more below), but in Navigator and the Mac version of Internet Explorer, bookmarks are stored in a single HTML file called Bookmarks.html (Navigator Mac), bookmark.htm (Navigator Windows), or Favorites.html (Internet Explorer Mac).

I suggest that you open up your bookmarks file in your favorite text editor and follow along as I explain how the file is put together. On a Mac, the Bookmarks.html or Favorites.html file is in the Preferences folder; browse inside the Netscape or Explorer folders located there. For Windows Navigator, look in the "Users" folder inside the Netscape program folder. The bookmark.htm file will be inside each user directory (for example, my bookmarks are located at

C:\Program Files\Netscape\Users\davidrugge\bookmark.htm

The HTML file begins with some header information giving the document type and a warning not to tamper with the bookmark file.

Next comes a level one header tag <H1>. In Navigator, this header denotes the name of the top-level folder within the Bookmarks window.

<H1>Bookmarks for David Rugge</H1>

Internet Explorer uses the level 1 header to describe the Favorites window itself. The header tag also contains additional attributes describing the location and size of the Favorites window, and whether it is open by default when Internet Explorer is launched.

<H1 WINDOW_POSITION="20,65" WINDOW_SIZE="350,250" WINDOW_OPEN="TRUE">Microsoft Internet Explorer</H1>

If you have subscribed to any of your favorites, this header also contains global subscription settings in the following attributes:

  • SUBSTATUS_POS: The screen coordinates at which the Subscription Status window will appear when subscriptions are being updated.

  • SUB_UPDATE_METHOD: Indicates which method to use to update subscriptions. A 0 indicates a manual update; 1 means update every time Internet Explorer is launched; 2 means update all subscriptions on a schedule determined by the values in SUB_UPDATE_UNIT, SUB_UPDATE_VALUE, and SUB_UPDATE_TIME.

  • SUB_UPDATE_UNIT: The unit, based on seconds, used to measure SUB_UPDATE_VALUE. Minutes are 60, hours 3600, and days 86400.

  • SUB_UPDATE_VALUE: Number of minutes, hours, or days to wait before updating all subscriptions (if Internet Explorer is on a timed schedule).

  • SUB_UPDATE_TIME: A time stamp (in seconds) used by Internet Explorer to figure out when to update the subscription (if updating on a timed schedule).

  • SOUND_NAME: Name of sound used to notify when all subscriptions are updated.

  • CUSTOM_NOTIFY: Appears if you checked the "custom notify" box in the subscriptions window. This option allows you to use sounds, an alert dialog box, flash the Explorer icon, and even send an email message when subscriptions are updated.

  • The following attributes appear if you checked the corresponding boxes in the Subscription Options window: PLAY_SOUND, DISPLAY_ALERT, FLASH_ICON, and SEND_MAIL.

  • USE_CUSTOM_ADDRESS: True if a custom email address is used for subscription notifications.

  • CUSTOM_ADDRESS: The custom email address to receive subscription information, or "" if a custom address is not used.

Folders and Bookmarks — Now come the bookmarks and bookmark folders. Folders and bookmarks are stored as a series of nested definition lists (the <DL> and </DL> tags).

Folders are level 3 headers in definition term tags:


Netscape has added a few attributes to the <H3> tag to make it easier to work with bookmarks in the Bookmarks window. The FOLDED attribute is added when a folder is collapsed, and is removed if the folder is closed. ADD_DATE, not surprisingly, contains a serial number representing the date when the folder was created. MENUHEADER marks this folder as the folder to use as the top level of the bookmark menu. NEWITEMHEADER indicates that this folder is where new bookmarks will first appear when they are created.

Internet Explorer for the Macintosh uses different attributes, e.g.:


  • WINDOW_POSITION: Position of the folder window.
  • WINDOW_SIZE: Size of the folder window when opened in pixels.
  • WINDOW_OPEN: True if the folder appears in a window when Internet Explorer is launched.
  • FOLDED: Same meaning as Navigator, above.

The actual bookmarks are anchors in definition term tags:

<DT><A HREF="" ADD_DATE="876146459" LAST_VISIT="882817020" LAST_MODIFIED="876230986">Yahoo</A>

Navigator has added its own attributes to the anchor tag <A> to keep track of various attributes of the bookmark. As you can see, these attributes are similar to the date attributes in the folder <H3> tags.

Navigator also allows the user to create aliases to folders or bookmarks. When an alias to a bookmark is created, the attribute ALIASID is added, which contains a number. The alias itself looks like a bookmark, but contains the additional attribute ALIASOF, which (surprise!) is equal to the ALIASID of the original bookmark that it refers to. For example:

Original bookmark:

<DT><A HREF="" ALIASID="2" ADD_DATE= "884557301" LAST_VISIT="884557291" LAST_MODIFIED="884557291"> NetBITS</A>

Bookmark alias:


ADD_DATE="884557301" LAST_VISIT="884557291" LAST_MODIFIED="884557291">NetBITS</A>

An alias will always have the same values for LAST_VISIT and LAST_MODIFIED as the original.

Internet Explorer uses the same general bookmark format (except it doesn’t support aliases), but includes some different attributes to track the status and subscription information for each favorite:

  • SUBSCRIBE: Appears if you have subscribed to this favorite

  • CHECK_LINKS_LEVEL: This appears in all new bookmarks. It is set to "" and doesn’t change in Internet Explorer 3 no matter what your settings are – I believe it’s related to an offline-browsing feature in Internet Explorer 4.

  • SOUND_NAME: The name of sound played when this favorite’s subscription is updated.

  • CUSTOM_NOTIFY: Appears if you checked the "custom notify" box in this favorite’s subscriptions window. This option enables you to assign custom notifications to each of your subscribed favorites so that you can tell them apart when they are updated. The options are the same as the global notifiers listed above in the <H1> header.

  • LAST_MODIFIED: A serial number representing the date the last time the page was changed.

  • LAST_MODIFIED_CHANGED: Appears if the page has changed since the last time you visited it or updated your subscriptions.

  • MESSAGE: Contains any messages about the status of the subscription. For example, it could contain "An error has occurred" if Internet Explorer failed to connect to the site the last time it updated your subscriptions.

Finally, dividers are delimited with the <HR> tag in Netscape, and with <DT><A HREF="">-</A> in Internet Explorer.

File Under F for File System — Microsoft, in its attempt to integrate the browser into the operating system, has chosen to use the Windows file system, rather than an HTML file, to store favorites for Internet Explorer. On the disk drive where the Windows system files reside, (usually C:) examine the contents of the directory C:\Windows\Favorites. Inside you will find Internet shortcut (.URL) files and folders corresponding to the folders and favorites in the Favorites window (or sidebar, depending on your configuration and browser version). Internet shortcuts are a special kind of shortcut that send a URL to the default browser. If you take a look at any one of the files in Notepad or your favorite text editor, it will look something like this:



The name of the Favorite corresponds to the file name of the Internet shortcut file. Internet Explorer uses the file attributes to find out the date the Favorite was created, the last time it was modified, and the last time it was used.

If you are using Internet Explorer 4, there will also be a Subscriptions folder in your Windows directory that contains one subscription file for each subscription. The Subscriptions folder is a special system folder, much like the Control Panels folder. You cannot open the subscription files in any program other than Internet Explorer, and trying to copy subscriptions out of the Subscriptions folder only creates an Internet shortcut to the subscription’s URL. Double-click a subscription file, and it acts exactly like an Internet shortcut. Right-clicking on a subscription file lets you update it or open its Properties window, where you can make more changes to the subscription’s settings. Windows will also let you add a subscription or change subscription settings if you right-click on an Internet shortcut.

Storage Methods — Each method of storing bookmarks has distinct advantages and disadvantages. Of the two formats, Internet Explorer favorites on Windows are more intuitive because they provide a consistent representation of the file and folder structure of your Favorites whether you view it from within the browser, Windows Explorer, or from the Windows file system. However, a hierarchy of files and folders is more difficult to move from computer to computer than a single HTML file, and since Internet Explorer for Windows is the only browser to use this format, it is also a lot less portable across browsers and operating systems.

This portability problem is exacerbated by the lack of a Favorites importing or exporting feature in Internet Explorer for Windows, which forces the user to turn to third-party bookmark conversion utilities. Also, if you have a few hundred bookmarks in your Favorites directory, these files and folders take up considerably more space on your hard drive than if they were collected in a single HTML bookmark file, especially on one gigabyte or larger hard disks using the older FAT16 file system. [Editor’s note: This problem is fixed by the Rev2 or OSR2 release of Windows 95, which is only available on machines sold in the last year and not as an upgrade. -Glenn]

To make matters worse, you can’t move your favorites or subscription settings between Mac and Windows versions of Internet Explorer. Maybe this is why Microsoft tells the Justice Department that the Mac and Windows versions of Internet Explorer really are separate products!

The big advantage of Navigator’s format is its portability. On a Macintosh, bookmark and favorite files can be used on either browser by simply renaming the file and putting it in the appropriate folder, or by using the import and export bookmarks options in Internet Explorer. Even if you decide to use a browser that does not support Netscape bookmarks, you can still open up the HTML file in your browser and follow the links. (The proprietary attributes that are added to the HTML tags should be ignored by any well-behaved browser.)

On the other hand, if you need to pass around groups of bookmarks, and do not know HTML, it is probably easier to attach a folder full of Favorites to an email message than to figure out which parts of the HTML bookmark file need to be pasted into the message. Also, the HTML bookmark format is less convenient to use than the individual favorites file format because you must use the bookmarks window within Navigator or an HTML editor to move, add, and delete bookmarks reliably. Unfortunately, Navigator does not provide an effective way of exporting its bookmark format into a Favorites folder.

Exchanging Information — Although both Netscape and Microsoft have taken pains to improve their bookmarking systems, the improvements have come mostly in the areas of user interface and organization and less in the area of interoperability. It is a shame that Netscape and Microsoft have not allowed for conversion from one bookmark format to the other, especially since it is not difficult to implement. Microsoft made an especially problematic decision when they made subscriptions and favorites incompatible between the Mac and Windows versions of Internet Explorer. Until Netscape and Microsoft get their act together, the only solution is to rely on third-party conversion tools or browsers like Opera, which thoughtfully supports the importing of either bookmark format.

[David Rugge lives in the greater Atlanta area and works at SunGard Recovery Services researching and testing for their Year 2000 project.]

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